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FAILED: patch "[PATCH] KVM: SVM: Add support for allowing zero SEV ASIDs" failed to apply to 6.1-stable tree

PATCH [email protected] 1 participant 1 message Apr 5, 2024

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The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 0aa6b90ef9d75b4bd7b6d106d85f2a3437697f91
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024040516-helmet-aware-9f06@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

0aa6b90ef9d7 ("KVM: SVM: Add support for allowing zero SEV ASIDs") 466eec4a22a7 ("KVM: SVM: Use unsigned integers when dealing with ASIDs") 106ed2cad9f7 ("KVM: SVM: WARN, but continue, if misc_cg_set_capacity() fails") 6d1bc9754b04 ("KVM: SVM: enhance info printk's in SEV init")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0aa6b90ef9d75b4bd7b6d106d85f2a3437697f91 Mon Sep 17 00:00:00 2001
From: Ashish Kalra <[email protected]>
Date: Wed, 31 Jan 2024 15:56:08 -0800
Subject: [PATCH] KVM: SVM: Add support for allowing zero SEV ASIDs

Some BIOSes allow the end user to set the minimum SEV ASID value (CPUID 0x8000001F_EDX) to be greater than the maximum number of encrypted guests, or maximum SEV ASID value (CPUID 0x8000001F_ECX) in order to dedicate all the SEV ASIDs to SEV-ES or SEV-SNP.

The SEV support, as coded, does not handle the case where the minimum SEV ASID value can be greater than the maximum SEV ASID value. As a result, the following confusing message is issued:

[   30.715724] kvm_amd: SEV enabled (ASIDs 1007 - 1006)

Fix the support to properly handle this case.

Fixes 916391a2d1dc ("KVM: SVM: Add support for SEV-ES capability in KVM")
Suggested-by Sean Christopherson <[email protected]>
Signed-off-by Ashish Kalra <[email protected]>
Cc [email protected]
Acked-by Tom Lendacky <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Sean Christopherson <[email protected]>
arch/x86/kvm/svm/sev.c +19 -10
index eeef43c795d8..5f8312edee36 100644
@@ -144,10 +144,21 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev)
 
 static int sev_asid_new(struct kvm_sev_info *sev)
 {
-	unsigned int asid, min_asid, max_asid;
+	/*
+	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
+	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
+	 * Note: min ASID can end up larger than the max if basic SEV support is
+	 * effectively disabled by disallowing use of ASIDs for SEV guests.
+	 */
+	unsigned int min_asid = sev->es_active ? 1 : min_sev_asid;
+	unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
+	unsigned int asid;
 	bool retry = true;
 	int ret;
 
+	if (min_asid > max_asid)
+		return -ENOTTY;
+
 	WARN_ON(sev->misc_cg);
 	sev->misc_cg = get_current_misc_cg();
 	ret = sev_misc_cg_try_charge(sev);

@@ -159,12 +170,6 @@ static int sev_asid_new(struct kvm_sev_info *sev)
 
 	mutex_lock(&sev_bitmap_lock);
 
-	/*
-	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
-	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
-	 */
-	min_asid = sev->es_active ? 1 : min_sev_asid;
-	max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
 again:
 	asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
 	if (asid > max_asid) {

@@ -2234,8 +2239,10 @@ void __init sev_hardware_setup(void)
 		goto out;
 	}
 
-	sev_asid_count = max_sev_asid - min_sev_asid + 1;
-	WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
+	if (min_sev_asid <= max_sev_asid) {
+		sev_asid_count = max_sev_asid - min_sev_asid + 1;
+		WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
+	}
 	sev_supported = true;
 
 	/* SEV-ES support requested? */

@@ -2266,7 +2273,9 @@ void __init sev_hardware_setup(void)
 out:
 	if (boot_cpu_has(X86_FEATURE_SEV))
 		pr_info("SEV %s (ASIDs %u - %u)\n",
-			sev_supported ? "enabled" : "disabled",
+			sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" :
+								       "unusable" :
+								       "disabled",
 			min_sev_asid, max_sev_asid);
 	if (boot_cpu_has(X86_FEATURE_SEV_ES))
 		pr_info("SEV-ES %s (ASIDs %u - %u)\n",