The patch titled
KVM: Fix segment state changes across processor mode switches
has been added to the -mm tree. Its filename is
kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: KVM: Fix segment state changes across processor mode switches
From: Yaniv Kamay <yaniv@xxxxxxxxxxxx>
A problem with Intel VT is that it performs very strict segment checks on
entry to vm86 mode. These checks are much stricter than what the cpu
actually allows for real mode, which is a problem since we use vm86 mode to
virtualize real mode.
The problem scenario is something like:
- switch to real mode
- here kvm mangles the segments to something that VT will like
- do something uninteresting
- switch to protected mode
- touch mangled segments
- blow up at unexpected values
Fix is as follows:
- switch to real mode
- mangle segments, but save original values somethere
- do something uninteresting
- switch to protected mode
- if segment selectors have not been changed, restore from saved values
- touch restored segments
- live happily ever after
Reported by: Simon Kagstrom <simon.kagstrom@xxxxxx>
Signed-off-by: Yaniv Kamay <yaniv@xxxxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/kvm/kvm.h | 3 ++-
drivers/kvm/kvm_main.c | 30 +++++++++++++++++++++++-------
2 files changed, 25 insertions(+), 8 deletions(-)
diff -puN drivers/kvm/kvm.h~kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches drivers/kvm/kvm.h
--- a/drivers/kvm/kvm.h~kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches
+++ a/drivers/kvm/kvm.h
@@ -191,10 +191,11 @@ struct kvm_vcpu {
int active;
u8 save_iopl;
struct {
+ u16 selector;
unsigned long base;
u32 limit;
u32 ar;
- } tr;
+ } tr, es, ds, fs, gs;
} rmode;
};
diff -puN drivers/kvm/kvm_main.c~kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches drivers/kvm/kvm_main.c
--- a/drivers/kvm/kvm_main.c~kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches
+++ a/drivers/kvm/kvm_main.c
@@ -704,18 +704,27 @@ static void enter_pmode(struct kvm_vcpu
update_exception_bitmap(vcpu);
#define FIX_PMODE_DATASEG(seg, save) { \
- vmcs_write16(GUEST_##seg##_SELECTOR, 0); \
- vmcs_writel(GUEST_##seg##_BASE, 0); \
- vmcs_write32(GUEST_##seg##_LIMIT, 0xffff); \
- vmcs_write32(GUEST_##seg##_AR_BYTES, 0x93); \
+ if (vmcs_readl(GUEST_##seg##_BASE) == save.base) { \
+ vmcs_write16(GUEST_##seg##_SELECTOR, save.selector); \
+ vmcs_writel(GUEST_##seg##_BASE, save.base); \
+ vmcs_write32(GUEST_##seg##_LIMIT, save.limit); \
+ vmcs_write32(GUEST_##seg##_AR_BYTES, save.ar); \
+ } else { \
+ u32 dpl = (vmcs_read16(GUEST_##seg##_SELECTOR) & \
+ SELECTOR_RPL_MASK) << AR_DPL_SHIFT; \
+ vmcs_write32(GUEST_##seg##_AR_BYTES, 0x93 | dpl); \
+ } \
}
- FIX_PMODE_DATASEG(SS, vcpu->rmode.ss);
FIX_PMODE_DATASEG(ES, vcpu->rmode.es);
FIX_PMODE_DATASEG(DS, vcpu->rmode.ds);
FIX_PMODE_DATASEG(GS, vcpu->rmode.gs);
FIX_PMODE_DATASEG(FS, vcpu->rmode.fs);
+
+ vmcs_write16(GUEST_SS_SELECTOR, 0);
+ vmcs_write32(GUEST_SS_AR_BYTES, 0x93);
+
vmcs_write16(GUEST_CS_SELECTOR,
vmcs_read16(GUEST_CS_SELECTOR) & ~SELECTOR_RPL_MASK);
vmcs_write32(GUEST_CS_AR_BYTES, 0x9b);
@@ -751,19 +760,26 @@ static void enter_rmode(struct kvm_vcpu
vmcs_writel(GUEST_CR4, vmcs_readl(GUEST_CR4) | CR4_VME_MASK);
update_exception_bitmap(vcpu);
- #define FIX_RMODE_SEG(seg, save) { \
+ #define FIX_RMODE_SEG(seg, save) { \
+ save.selector = vmcs_read16(GUEST_##seg##_SELECTOR); \
+ save.base = vmcs_readl(GUEST_##seg##_BASE); \
+ save.limit = vmcs_read32(GUEST_##seg##_LIMIT); \
+ save.ar = vmcs_read32(GUEST_##seg##_AR_BYTES); \
vmcs_write16(GUEST_##seg##_SELECTOR, \
vmcs_readl(GUEST_##seg##_BASE) >> 4); \
vmcs_write32(GUEST_##seg##_LIMIT, 0xffff); \
vmcs_write32(GUEST_##seg##_AR_BYTES, 0xf3); \
}
+ vmcs_write16(GUEST_SS_SELECTOR, vmcs_readl(GUEST_SS_BASE) >> 4);
+ vmcs_write32(GUEST_SS_LIMIT, 0xffff);
+ vmcs_write32(GUEST_SS_AR_BYTES, 0xf3);
+
vmcs_write32(GUEST_CS_AR_BYTES, 0xf3);
vmcs_write16(GUEST_CS_SELECTOR, vmcs_readl(GUEST_CS_BASE) >> 4);
FIX_RMODE_SEG(ES, vcpu->rmode.es);
FIX_RMODE_SEG(DS, vcpu->rmode.ds);
- FIX_RMODE_SEG(SS, vcpu->rmode.ss);
FIX_RMODE_SEG(GS, vcpu->rmode.gs);
FIX_RMODE_SEG(FS, vcpu->rmode.fs);
}
_
Patches currently in -mm which might be from yaniv@xxxxxxxxxxxx are
kvm-userspace-interface.patch
kvm-intel-virtual-mode-extensions-definitions.patch
kvm-kvm-data-structures.patch
kvm-random-accessors-and-constants.patch
kvm-virtualization-infrastructure.patch
kvm-virtualization-infrastructure-fix-segment-state-changes-across-processor-mode-switches.patch
kvm-memory-slot-management.patch
kvm-vcpu-creation-and-maintenance.patch
kvm-vcpu-execution-loop.patch
kvm-define-exit-handlers.patch
kvm-less-common-exit-handlers.patch
kvm-mmu.patch
kvm-x86-emulator.patch
-
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