queue-6.1/kvm-svm-add-support-for-allowing-zero-sev-asids.patch

   1 From 0ab1837687c5503e2cb43ec4dfacde6e12f0ff20 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Wed, 31 Jan 2024 15:56:08 -0800
   4 Subject: KVM: SVM: Add support for allowing zero SEV ASIDs
   5
   6 From: Ashish Kalra <ashish.kalra@amd.com>
   7
   8 [ Upstream commit 0aa6b90ef9d75b4bd7b6d106d85f2a3437697f91 ]
   9
  10 Some BIOSes allow the end user to set the minimum SEV ASID value
  11 (CPUID 0x8000001F_EDX) to be greater than the maximum number of
  12 encrypted guests, or maximum SEV ASID value (CPUID 0x8000001F_ECX)
  13 in order to dedicate all the SEV ASIDs to SEV-ES or SEV-SNP.
  14
  15 The SEV support, as coded, does not handle the case where the minimum
  16 SEV ASID value can be greater than the maximum SEV ASID value.
  17 As a result, the following confusing message is issued:
  18
  19 [   30.715724] kvm_amd: SEV enabled (ASIDs 1007 - 1006)
  20
  21 Fix the support to properly handle this case.
  22
  23 Fixes: 916391a2d1dc ("KVM: SVM: Add support for SEV-ES capability in KVM")
  24 Suggested-by: Sean Christopherson <seanjc@google.com>
  25 Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
  26 Cc: stable@vger.kernel.org
  27 Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
  28 Link: https://lore.kernel.org/r/20240104190520.62510-1-Ashish.Kalra@amd.com
  29 Link: https://lore.kernel.org/r/20240131235609.4161407-4-seanjc@google.com
  30 Signed-off-by: Sean Christopherson <seanjc@google.com>
  31 Signed-off-by: Sasha Levin <sashal@kernel.org>
  32 ---
  33  arch/x86/kvm/svm/sev.c | 29 +++++++++++++++++++----------
  34  1 file changed, 19 insertions(+), 10 deletions(-)
  35
  36 diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
  37 index 9e50eaf967f22..d8e192ad59538 100644
  38 --- a/arch/x86/kvm/svm/sev.c
  39 +++ b/arch/x86/kvm/svm/sev.c
  40 @@ -136,10 +136,21 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev)
  41
  42  static int sev_asid_new(struct kvm_sev_info *sev)
  43  {
  44 -       unsigned int asid, min_asid, max_asid;
  45 +       /*
  46 +        * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
  47 +        * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
  48 +        * Note: min ASID can end up larger than the max if basic SEV support is
  49 +        * effectively disabled by disallowing use of ASIDs for SEV guests.
  50 +        */
  51 +       unsigned int min_asid = sev->es_active ? 1 : min_sev_asid;
  52 +       unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
  53 +       unsigned int asid;
  54         bool retry = true;
  55         int ret;
  56
  57 +       if (min_asid > max_asid)
  58 +               return -ENOTTY;
  59 +
  60         WARN_ON(sev->misc_cg);
  61         sev->misc_cg = get_current_misc_cg();
  62         ret = sev_misc_cg_try_charge(sev);
  63 @@ -151,12 +162,6 @@ static int sev_asid_new(struct kvm_sev_info *sev)
  64
  65         mutex_lock(&sev_bitmap_lock);
  66
  67 -       /*
  68 -        * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
  69 -        * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
  70 -        */
  71 -       min_asid = sev->es_active ? 1 : min_sev_asid;
  72 -       max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
  73  again:
  74         asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
  75         if (asid > max_asid) {
  76 @@ -2215,8 +2220,10 @@ void __init sev_hardware_setup(void)
  77                 goto out;
  78         }
  79
  80 -       sev_asid_count = max_sev_asid - min_sev_asid + 1;
  81 -       WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
  82 +       if (min_sev_asid <= max_sev_asid) {
  83 +               sev_asid_count = max_sev_asid - min_sev_asid + 1;
  84 +               WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
  85 +       }
  86         sev_supported = true;
  87
  88         /* SEV-ES support requested? */
  89 @@ -2247,7 +2254,9 @@ void __init sev_hardware_setup(void)
  90  out:
  91         if (boot_cpu_has(X86_FEATURE_SEV))
  92                 pr_info("SEV %s (ASIDs %u - %u)\n",
  93 -                       sev_supported ? "enabled" : "disabled",
  94 +                       sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" :
  95 +                                                                      "unusable" :
  96 +                                                                      "disabled",
  97                         min_sev_asid, max_sev_asid);
  98         if (boot_cpu_has(X86_FEATURE_SEV_ES))
  99                 pr_info("SEV-ES %s (ASIDs %u - %u)\n",
 100 --
 101 2.43.0
 102