diff options
| author | Yang Zhong <yang.zhong@intel.com> | 2022-02-16 22:04:29 -0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-03-15 11:50:50 +0100 |
| commit | 19db68ca68a78fa033a21d419036b6e416554564 (patch) | |
| tree | d253b2ac5ff2edc70ac2baf80be2a59c320292d8 /target/i386/cpu.c | |
| parent | 1f16764f7d4515bfd5e4ae0aae814fa280a7d0c8 (diff) | |
x86: Grant AMX permission for guest
Kernel allocates 4K xstate buffer by default. For XSAVE features
which require large state component (e.g. AMX), Linux kernel
dynamically expands the xstate buffer only after the process has
acquired the necessary permissions. Those are called dynamically-
enabled XSAVE features (or dynamic xfeatures).
There are separate permissions for native tasks and guests.
Qemu should request the guest permissions for dynamic xfeatures
which will be exposed to the guest. This only needs to be done
once before the first vcpu is created.
KVM implemented one new ARCH_GET_XCOMP_SUPP system attribute API to
get host side supported_xcr0 and Qemu can decide if it can request
dynamically enabled XSAVE features permission.
https://lore.kernel.org/all/20220126152210.3044876-1-pbonzini@redhat.com/
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Message-Id: <20220217060434.52460-4-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'target/i386/cpu.c')
| -rw-r--r-- | target/i386/cpu.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/target/i386/cpu.c b/target/i386/cpu.c index ec35dd1717..505ee289bc 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -6007,6 +6007,7 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu) CPUX86State *env = &cpu->env; int i; uint64_t mask; + static bool request_perm; if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) { env->features[FEAT_XSAVE_COMP_LO] = 0; @@ -6022,6 +6023,12 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu) } } + /* Only request permission for first vcpu */ + if (kvm_enabled() && !request_perm) { + kvm_request_xsave_components(cpu, mask); + request_perm = true; + } + env->features[FEAT_XSAVE_COMP_LO] = mask; env->features[FEAT_XSAVE_COMP_HI] = mask >> 32; } |