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| author | Lai Jiangshan <jiangshan.ljs@antgroup.com> | 2022-03-11 08:03:44 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-04-02 11:34:43 +0200 |
| commit | 4f4aa80e3b882cbbafdf95ebc018c72b10879dbb (patch) | |
| tree | 776d39bacece84f6fca92040b035fb65af663047 /arch/x86/kvm/x86.c | |
| parent | KVM: X86: Rename variable smap to not_smap in permission_fault() (diff) | |
| download | linux-4f4aa80e3b882cbbafdf95ebc018c72b10879dbb.tar.xz linux-4f4aa80e3b882cbbafdf95ebc018c72b10879dbb.zip | |
KVM: X86: Handle implicit supervisor access with SMAP
There are two kinds of implicit supervisor access
implicit supervisor access when CPL = 3
implicit supervisor access when CPL < 3
Current permission_fault() handles only the first kind for SMAP.
But if the access is implicit when SMAP is on, data may not be read
nor write from any user-mode address regardless the current CPL.
So the second kind should be also supported.
The first kind can be detect via CPL and access mode: if it is
supervisor access and CPL = 3, it must be implicit supervisor access.
But it is not possible to detect the second kind without extra
information, so this patch adds an artificial PFERR_EXPLICIT_ACCESS
into @access. This extra information also works for the first kind, so
the logic is changed to use this information for both cases.
The value of PFERR_EXPLICIT_ACCESS is deliberately chosen to be bit 48
which is in the most significant 16 bits of u64 and less likely to be
forced to change due to future hardware uses it.
This patch removes the call to ->get_cpl() for access mode is determined
by @access. Not only does it reduce a function call, but also remove
confusions when the permission is checked for nested TDP. The nested
TDP shouldn't have SMAP checking nor even the L2's CPL have any bearing
on it. The original code works just because it is always user walk for
NPT and SMAP fault is not set for EPT in update_permission_bitmask.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Message-Id: <20220311070346.45023-5-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kvm/x86.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5c5be7a63b9f..a43026bac138 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6865,7 +6865,9 @@ static int emulator_read_std(struct x86_emulate_ctxt *ctxt, struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); u64 access = 0; - if (!system && static_call(kvm_x86_get_cpl)(vcpu) == 3) + if (system) + access |= PFERR_IMPLICIT_ACCESS; + else if (static_call(kvm_x86_get_cpl)(vcpu) == 3) access |= PFERR_USER_MASK; return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access, exception); @@ -6917,7 +6919,9 @@ static int emulator_write_std(struct x86_emulate_ctxt *ctxt, gva_t addr, void *v struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); u64 access = PFERR_WRITE_MASK; - if (!system && static_call(kvm_x86_get_cpl)(vcpu) == 3) + if (system) + access |= PFERR_IMPLICIT_ACCESS; + else if (static_call(kvm_x86_get_cpl)(vcpu) == 3) access |= PFERR_USER_MASK; return kvm_write_guest_virt_helper(addr, val, bytes, vcpu, |