diff options
Diffstat (limited to '0011-x86-cpu-policy-Fix-migration-from-Ice-Lake-to-Cascad.patch')
| -rw-r--r-- | 0011-x86-cpu-policy-Fix-migration-from-Ice-Lake-to-Cascad.patch | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/0011-x86-cpu-policy-Fix-migration-from-Ice-Lake-to-Cascad.patch b/0011-x86-cpu-policy-Fix-migration-from-Ice-Lake-to-Cascad.patch new file mode 100644 index 0000000..26eb3ec --- /dev/null +++ b/0011-x86-cpu-policy-Fix-migration-from-Ice-Lake-to-Cascad.patch @@ -0,0 +1,92 @@ +From 0673eae8e53de5007dba35149527579819428323 Mon Sep 17 00:00:00 2001 +From: Andrew Cooper <andrew.cooper3@citrix.com> +Date: Tue, 21 May 2024 10:22:08 +0200 +Subject: [PATCH 11/56] x86/cpu-policy: Fix migration from Ice Lake to Cascade + Lake +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Ever since Xen 4.14, there has been a latent bug with migration. + +While some toolstacks can level the features properly, they don't shink +feat.max_subleaf when all features have been dropped. This is because +we *still* have not completed the toolstack side work for full CPU Policy +objects. + +As a consequence, even when properly feature levelled, VMs can't migrate +"backwards" across hardware which reduces feat.max_subleaf. One such example +is Ice Lake (max_subleaf=2 for INTEL_PSFD) to Cascade Lake (max_subleaf=0). + +Extend the max policies feat.max_subleaf to the hightest number Xen knows +about, but leave the default policies matching the host. This will allow VMs +with a higher feat.max_subleaf than strictly necessary to migrate in. + +Eventually we'll manage to teach the toolstack how to avoid creating such VMs +in the first place, but there's still more work to do there. + +Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> +Acked-by: Roger Pau Monné <roger.pau@citrix.com> +master commit: a2330b51df267e20e66bbba6c5bf08f0570ed58b +master date: 2024-05-07 16:56:46 +0100 +--- + xen/arch/x86/cpu-policy.c | 22 ++++++++++++++++++++++ + 1 file changed, 22 insertions(+) + +diff --git a/xen/arch/x86/cpu-policy.c b/xen/arch/x86/cpu-policy.c +index a822800f52..1aba6ed4ca 100644 +--- a/xen/arch/x86/cpu-policy.c ++++ b/xen/arch/x86/cpu-policy.c +@@ -603,6 +603,13 @@ static void __init calculate_pv_max_policy(void) + unsigned int i; + + *p = host_cpu_policy; ++ ++ /* ++ * Some VMs may have a larger-than-necessary feat max_subleaf. Allow them ++ * to migrate in. ++ */ ++ p->feat.max_subleaf = ARRAY_SIZE(p->feat.raw) - 1; ++ + x86_cpu_policy_to_featureset(p, fs); + + for ( i = 0; i < ARRAY_SIZE(fs); ++i ) +@@ -643,6 +650,10 @@ static void __init calculate_pv_def_policy(void) + unsigned int i; + + *p = pv_max_cpu_policy; ++ ++ /* Default to the same max_subleaf as the host. */ ++ p->feat.max_subleaf = host_cpu_policy.feat.max_subleaf; ++ + x86_cpu_policy_to_featureset(p, fs); + + for ( i = 0; i < ARRAY_SIZE(fs); ++i ) +@@ -679,6 +690,13 @@ static void __init calculate_hvm_max_policy(void) + const uint32_t *mask; + + *p = host_cpu_policy; ++ ++ /* ++ * Some VMs may have a larger-than-necessary feat max_subleaf. Allow them ++ * to migrate in. ++ */ ++ p->feat.max_subleaf = ARRAY_SIZE(p->feat.raw) - 1; ++ + x86_cpu_policy_to_featureset(p, fs); + + mask = hvm_hap_supported() ? +@@ -780,6 +798,10 @@ static void __init calculate_hvm_def_policy(void) + const uint32_t *mask; + + *p = hvm_max_cpu_policy; ++ ++ /* Default to the same max_subleaf as the host. */ ++ p->feat.max_subleaf = host_cpu_policy.feat.max_subleaf; ++ + x86_cpu_policy_to_featureset(p, fs); + + mask = hvm_hap_supported() ? +-- +2.45.2 + |