target-i386: Sanity check host processor physical address width
PATCH 1/1 target-i386: Sanity check host processor physical address width
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)
linux-headers/linux/kvm.h +1 -0
@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING
target-i386/kvm.c +6 -0
@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {
@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);
Signature · 1 line
2.4.3
Quoted 41 lines · Bandan Das
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +1
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) }
target-i386/kvm.c int kvm_arch_init(MachineState *ms, KVMState *s) · line 956
Quoted 10 lines
target-i386/kvm.c +5
-0} + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);
First, see my comments on the KVM patch.
Second, ram_size is not the right thing to compare. What should be checked is whether the highest guest-physical address that maps to RAM can be represented in the address width of the host processor (and only if EPT is enabled, but that sub-condition belongs to the KVM patch).
Note that this is not the same as the check written in the patch. For example, if you assume a 32-bit PCI hole with size 1 GB, then a total guest RAM of size 63 GB will result in the highest guest-phys memory address being 0xF_FFFF_FFFF, which just fits into 36 bits.
Correspondingly, the above code would not print the warning for
-m $((63 * 1024 + 1))
on my laptop (which has "address sizes : 36 bits physical, ..."), even
though such a guest would not boot for me (with EPT enabled).
Please see
http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447
So, "ram_size" in the controlling expression should be replaced with "maximum_guest_ram_address" (which should be inclusive, and the <= relop should be preserved).
Thanks
Laszlo
Quoted 72 lines · On Thu, 09 Jul 2015 09:02:38 +0200 Laszlo Ersek <[email protected]> wrote:
Quoted 41 lines · Bandan Das
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +1
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) }target-i386/kvm.c int kvm_arch_init(MachineState *ms, KVMState *s) · line 956
Quoted 10 lines
target-i386/kvm.c +5
-0} + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);First, see my comments on the KVM patch.
Second,
ram_sizeis not the right thing to compare. What should be checked is whether the highest guest-physical address that maps to RAM can be represented in the address width of the host processor (and only if EPT is enabled, but that sub-condition belongs to the KVM patch).Note that this is not the same as the check written in the patch. For example, if you assume a 32-bit PCI hole with size 1 GB, then a total guest RAM of size 63 GB will result in the highest guest-phys memory address being 0xF_FFFF_FFFF, which just fits into 36 bits.
Correspondingly, the above code would not print the warning for
-m $((63 * 1024 + 1))on my laptop (which has "address sizes : 36 bits physical, ..."), even
though such a guest would not boot for me (with EPT enabled).
Quoted 7 lines
Please see
http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447
So, "
ram_size" in the controlling expression should be replaced with "maximum_guest_ram_address" (which should be inclusive, and the <= relop should be preserved).
also with memory hotplug tuned on we should check if the end of hotplug memory area is less then limit, i.e.:
pcms->hotplug_memory.base + hotplug_mem_size < 1ULL << max_phys_bits
Quoted 4 lines
Thanks
Laszlo
Quoted 79 lines · Igor Mammedov
Quoted 76 lines · On Thu, 09 Jul 2015 09:02:38 +0200 Laszlo Ersek <[email protected]> wrote:
Quoted 41 lines · Bandan Das
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +1
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) }target-i386/kvm.c int kvm_arch_init(MachineState *ms, KVMState *s) · line 956
Quoted 10 lines
target-i386/kvm.c +5
-0} + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);First, see my comments on the KVM patch.
Second,
ram_sizeis not the right thing to compare. What should be checked is whether the highest guest-physical address that maps to RAM can be represented in the address width of the host processor (and only if EPT is enabled, but that sub-condition belongs to the KVM patch).Note that this is not the same as the check written in the patch. For example, if you assume a 32-bit PCI hole with size 1 GB, then a total guest RAM of size 63 GB will result in the highest guest-phys memory address being 0xF_FFFF_FFFF, which just fits into 36 bits.
Correspondingly, the above code would not print the warning for
-m $((63 * 1024 + 1))on my laptop (which has "address sizes : 36 bits physical, ..."), even
though such a guest would not boot for me (with EPT enabled).Please see
http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447
Quoted 7 lines
Quoted 3 lines
So, "
ram_size" in the controlling expression should be replaced with "maximum_guest_ram_address" (which should be inclusive, and the <= relop should be preserved).also with memory hotplug tuned on we should check if the end of hotplug memory area is less then limit, i.e.:
pcms->hotplug_memory.base+hotplug_mem_size< 1ULL <<max_phys_bits
Seems reasonable, thanks for the hint!
(The LHS in this instance is exclusive though, so equality should *not* trigger the warning. "maximum_guest_ram_address" is inclusive, and equality should trigger the warning. (Although equality seems quite impossible in practice.))
Thanks!
Laszlo
Laszlo Ersek <[email protected]> writes:
...
Quoted 27 lines
Quoted 27 lines
Quoted 27 lines
First, see my comments on the KVM patch.
Second,
ram_sizeis not the right thing to compare. What should be checked is whether the highest guest-physical address that maps to RAM can be represented in the address width of the host processor (and only if EPT is enabled, but that sub-condition belongs to the KVM patch).Note that this is not the same as the check written in the patch. For example, if you assume a 32-bit PCI hole with size 1 GB, then a total guest RAM of size 63 GB will result in the highest guest-phys memory address being 0xF_FFFF_FFFF, which just fits into 36 bits.
Correspondingly, the above code would not print the warning for
-m $((63 * 1024 + 1))on my laptop (which has "address sizes : 36 bits physical, ..."), even
though such a guest would not boot for me (with EPT enabled).Please see
http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447
So, "
ram_size" in the controlling expression should be replaced with "maximum_guest_ram_address" (which should be inclusive, and the <= relop should be preserved).
Quoted 6 lines
Quoted 4 lines
also with memory hotplug tuned on we should check if the end of hotplug memory area is less then limit, i.e.:
pcms->hotplug_memory.base+hotplug_mem_size< 1ULL <<max_phys_bitsSeems reasonable, thanks for the hint!
Thanks Igor and Laszlo, makes sense. I am wondering if this 1GB PCI hole is always fixed so that I can simply include that in calculating the maximum guest ram address ? Or do we have to figure that out every time ?
Quoted 7 lines
(The LHS in this instance is exclusive though, so equality should *not* trigger the warning. "
maximum_guest_ram_address" is inclusive, and equality should trigger the warning. (Although equality seems quite impossible in practice.))Thanks!
Laszlo
Quoted 32 lines · Bandan Das
Laszlo Ersek <[email protected]> writes:
...Quoted 30 lines
Quoted 30 lines
Quoted 20 lines
First, see my comments on the KVM patch.
Second,
ram_sizeis not the right thing to compare. What should be checked is whether the highest guest-physical address that maps to RAM can be represented in the address width of the host processor (and only if EPT is enabled, but that sub-condition belongs to the KVM patch).Note that this is not the same as the check written in the patch. For example, if you assume a 32-bit PCI hole with size 1 GB, then a total guest RAM of size 63 GB will result in the highest guest-phys memory address being 0xF_FFFF_FFFF, which just fits into 36 bits.
Correspondingly, the above code would not print the warning for
-m $((63 * 1024 + 1))on my laptop (which has "address sizes : 36 bits physical, ..."), even
though such a guest would not boot for me (with EPT enabled).Quoted 7 lines
Please see
http://thread.gmane.org/gmane.comp.bios.tianocore.devel/15418/focus=15447
So, "
ram_size" in the controlling expression should be replaced with "maximum_guest_ram_address" (which should be inclusive, and the <= relop should be preserved).also with memory hotplug tuned on we should check if the end of hotplug memory area is less then limit, i.e.:
Quoted 7 lines
Quoted 3 lines
Quoted 1 line
pcms->hotplug_memory.base+hotplug_mem_size< 1ULL <<max_phys_bitsSeems reasonable, thanks for the hint!
Thanks Igor and Laszlo, makes sense. I am wondering if this 1GB PCI hole is always fixed so that I can simply include that in calculating the maximum guest ram address ? Or do we have to figure that out every time ?
Please grep the tree for "above_4g_mem_size". The size of the 32-bit PCI hole is not constant, but all the necessary computation goes into "above_4g_mem_size" already.
So I think you should derive the max possible gpa from "above_4g_mem_size" and the top of the hotpluggable memory area, and compare that against the PCPU address width, *if* EPT is enabled.
(BTW "pcms->hotplug_memory.base" depends on "above_4g_mem_size" too.)
Thanks
Laszlo
Quoted 8 lines
Quoted 8 lines
(The LHS in this instance is exclusive though, so equality should *not* trigger the warning. "
maximum_guest_ram_address" is inclusive, and equality should trigger the warning. (Although equality seems quite impossible in practice.))Thanks!
Laszlo
Paolo Bonzini
maintainerQuoted 9 lines · Bandan Das
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>
This is not entirely correct, because it doesn't take the PCI hole into account.
Perhaps KVM could simply hide memory above the limit (i.e. treat it as MMIO), and the BIOS could remove RAM above the limit from the e820 memory map?
Paolo
Quoted 42 lines
--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +6
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);
Quoted 13 lines · Paolo Bonzini
Quoted 9 lines · Bandan Das
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>
Quoted 6 lines
This is not entirely correct, because it doesn't take the PCI hole into account.
Perhaps KVM could simply hide memory above the limit (i.e. treat it as MMIO), and the BIOS could remove RAM above the limit from the e820 memory map?
I'd prefer to leave the guest firmware*s* out of this... :)
E820 is a legacy BIOS concept. In OVMF we'd have to hack the memory resource descriptor HOBs (which in turn control the DXE memory space map, which in turn controls the UEFI memory map). Those HOBs are currently based on what the CMOS reports about the RAM available under and above 4GB.
It's pretty complex already (will get more complex with SMM support), and TBH, for working around such an obscure issue, I wouldn't like to complicate it even further...
After all, this is a host platform limitation. The solution should be to either move to a more capable host, or do it in software (disable EPT).
Thanks!
Laszlo
Quoted 45 lines
Paolo
Quoted 42 lines
--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +6
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH ); +if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);
Paolo Bonzini
maintainerQuoted 12 lines · Laszlo Ersek
Quoted 4 lines
Quoted 4 lines
Perhaps KVM could simply hide memory above the limit (i.e. treat it as MMIO), and the BIOS could remove RAM above the limit from the e820 memory map?
I'd prefer to leave the guest firmware*s* out of this... :)
E820 is a legacy BIOS concept. In OVMF we'd have to hack the memory resource descriptor HOBs (which in turn control the DXE memory space map, which in turn controls the UEFI memory map). Those HOBs are currently based on what the CMOS reports about the RAM available under and above 4GB.
Quoted 6 lines
It's pretty complex already (will get more complex with SMM support), and TBH, for working around such an obscure issue, I wouldn't like to complicate it even further...
After all, this is a host platform limitation. The solution should be to either move to a more capable host, or do it in software (disable EPT).
The reason I mentioned the firmware is because you could in principle have the same issue on real hardware - say putting 128 GB on your laptop. The firmware should cope with it.
If OVMF does not use etc/e820, it can instead hack the values it reads from CMOS, bounding them according to the CPUID value.
Paolo
Quoted 17 lines · Paolo Bonzini
Quoted 16 lines · Laszlo Ersek
Quoted 4 lines
Quoted 4 lines
Perhaps KVM could simply hide memory above the limit (i.e. treat it as MMIO), and the BIOS could remove RAM above the limit from the e820 memory map?
I'd prefer to leave the guest firmware*s* out of this... :)
E820 is a legacy BIOS concept. In OVMF we'd have to hack the memory resource descriptor HOBs (which in turn control the DXE memory space map, which in turn controls the UEFI memory map). Those HOBs are currently based on what the CMOS reports about the RAM available under and above 4GB.
It's pretty complex already (will get more complex with SMM support), and TBH, for working around such an obscure issue, I wouldn't like to complicate it even further...
Quoted 6 lines
Quoted 2 lines
After all, this is a host platform limitation. The solution should be to either move to a more capable host, or do it in software (disable EPT).
The reason I mentioned the firmware is because you could in principle have the same issue on real hardware - say putting 128 GB on your laptop. The firmware should cope with it.
Agreed, it's probably not a good idea to deviate too much from how real hardware would behave IMO. As a simplification of Paolo's idea, is it possible for qemu to completely ignore memory above the limit ? Will that break anything ? :)
Quoted 4 lines
If OVMF does not use etc/e820, it can instead hack the values it reads from CMOS, bounding them according to the CPUID value.
Paolo
Quoted 39 lines · On Wed, 08 Jul 2015 18:42:01 -0400 Bandan Das <[email protected]> wrote:
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +1
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {
target-i386/kvm.c int kvm_arch_init(MachineState *ms, KVMState *s) · line 949
Quoted 4 lines
target-i386/kvm.c +1
-0@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH );
max_phys_bits seems generic enough and could be applied to other targets as well.
making it a property of machine, would make accessing/manipulating it easier. define default value for machine/TCG mode and when KVM is enabled it would override/set its own limit.
then any board could easily access machine->max_gpa to make board specific checks.
Quoted 7 lines
target-i386/kvm.c +4
-0+if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);
Quoted 45 lines · Igor Mammedov
Quoted 42 lines · On Wed, 08 Jul 2015 18:42:01 -0400 Bandan Das <[email protected]> wrote:
If a Linux guest is assigned more memory than is supported by the host processor, the guest is unable to boot. That is expected, however, there's no message indicating the user what went wrong. This change prints a message to stderr if KVM has the corresponding capability.
Reported-by Laszlo Ersek <[email protected]>Signed-off-by Bandan Das <[email protected]>--- linux-headers/linux/kvm.h | 1 + target-i386/kvm.c | 6 ++++++ 2 files changed, 7 insertions(+)linux-headers/linux/kvm.h +1
-0@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {#define KVM_CAP_DISABLE_QUIRKS 116#define KVM_CAP_X86_SMM 117#define KVM_CAP_MULTI_ADDRESS_SPACE 118 +#define KVM_CAP_PHY_ADDR_WIDTH 119#ifdef KVM_CAP_IRQ_ROUTING target-i386/kvm.c +1
-0@@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)uint64_t shadow_mem;int ret;struct utsname utsname; +int max_phys_bits; ret =kvm_get_supported_msrs (s);if (ret <0 ) {@@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } }
Quoted 3 lines
target-i386/kvm.c int kvm_arch_init(MachineState *ms, KVMState *s) · line 949
Quoted 1 line
target-i386/kvm.c +1
-0+ max_phys_bits =kvm_check_extension (s,KVM_CAP_PHY_ADDR_WIDTH );
max_phys_bitsseems generic enough and could be applied to other targets as well.
I am a little clueless about other targets but is figuring this out from userspace as simple as it's on x86 (cpuid)? If not, then I agree, this could be made a generic value.
Bandan
Quoted 14 lines
making it a property of machine, would make accessing/manipulating it easier. define default value for machine/TCG mode and when KVM is enabled it would override/set its own limit.
then any board could easily access
machine->max_gpato make board specific checks.Quoted 7 lines
target-i386/kvm.c +4
-0+if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size) +fprintf (stderr,"Warning: The amount of memory assigned to the guest " +"is more than that supported by the host CPU(s). Guest may be unstable.\n" ); +if (kvm_check_extension (s,KVM_CAP_X86_SMM )) { smram_machine_done.notify = register_smram_listener;qemu_add_machine_init_done_notifier (&smram_machine_done);