* [PATCH v6 1/2] xen/hvm: introduce a flags field in the CPU save record
2016-01-12 16:12 [PATCH v6 0/2] Introduce a flags field to HVM CPU context Roger Pau Monne
@ 2016-01-12 16:12 ` Roger Pau Monne
2016-01-12 16:31 ` Jan Beulich
2016-01-12 16:12 ` [PATCH v6 2/2] Revert "libxc: create an initial FPU state for HVM guests" Roger Pau Monne
1 sibling, 1 reply; 6+ messages in thread
From: Roger Pau Monne @ 2016-01-12 16:12 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Jan Beulich, Roger Pau Monne
Introduce a new flags field and use bit 0 to signal if the FPU has been
initialised or not. Previously Xen always wrongly assumed the FPU was
initialised on restore.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
---
Changes since v5:
- Adapt the code due to the changes introduced by XSA-165.
Changes since v4:
- Zero the fpu save area if the FPU is not initialised. This avoids
leaking hypervisor data.
- Due to the previous patch in this series, slightly rework the way to load
the FPU state in a xsave capable host.
Changes since v3:
- Don't add a comment in the compat structure regaring the fpu_initialised
field.
- Rename fpu_initialised to flags and use it as a bit field. Bit 0 will be
used to signal whether the fpu is initialised.
- Only save the fpu context if it's initialised.
- Only restore the fpu context from the save record if the fpu is
initialised.
- Check that unused bits in the flags field are 0.
Changes since v1:
- Don't add yet another compat structure, new fields should always be added
to the end of the existing structure and offsetof should be used to
compare sizes.
- Leave the previous compat structure as-is, since the field was not added
to the end we cannot remove it and use offsetof in this case.
- Set xstate_bv based on fpu_initialised value instead of unconditionally
setting it to XSTATE_FP_SSE.
---
xen/arch/x86/hvm/hvm.c | 42 ++++++++++++++++++++++------------
xen/include/public/arch-x86/hvm/save.h | 27 ++++++++++++++++------
2 files changed, 48 insertions(+), 21 deletions(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 787b7de..79ec90f 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1797,9 +1797,15 @@ static int hvm_save_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
ctxt.ldtr_arbytes = seg.attr.bytes;
if ( v->fpu_initialised )
+ {
memcpy(ctxt.fpu_regs, v->arch.fpu_ctxt, sizeof(ctxt.fpu_regs));
- else
- memset(ctxt.fpu_regs, 0, sizeof(ctxt.fpu_regs));
+ ctxt.flags = XEN_X86_FPU_INITIALISED;
+ }
+ else
+ {
+ memset(ctxt.fpu_regs, 0, sizeof(ctxt.fpu_regs));
+ ctxt.flags = 0;
+ }
ctxt.rax = v->arch.user_regs.eax;
ctxt.rbx = v->arch.user_regs.ebx;
@@ -1981,7 +1987,7 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
return -EINVAL;
}
- if ( hvm_load_entry(CPU, h, &ctxt) != 0 )
+ if ( hvm_load_entry_zeroextend(CPU, h, &ctxt) != 0 )
return -EINVAL;
/* Sanity check some control registers. */
@@ -2009,6 +2015,13 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
return -EINVAL;
}
+ if ( (ctxt.flags & ~XEN_X86_FPU_INITIALISED) != 0 )
+ {
+ gprintk(XENLOG_ERR, "bad flags value in CPU context: %#x\n",
+ ctxt.flags);
+ return -EINVAL;
+ }
+
/* Older Xen versions used to save the segment arbytes directly
* from the VMCS on Intel hosts. Detect this and rearrange them
* into the struct segment_register format. */
@@ -2087,19 +2100,21 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
seg.attr.bytes = ctxt.ldtr_arbytes;
hvm_set_segment_register(v, x86_seg_ldtr, &seg);
- /* In case xsave-absent save file is restored on a xsave-capable host */
- if ( cpu_has_xsave && !xsave_enabled(v) )
+ v->fpu_initialised = !!(ctxt.flags & XEN_X86_FPU_INITIALISED);
+ if ( v->fpu_initialised )
{
- struct xsave_struct *xsave_area = v->arch.xsave_area;
+ memcpy(v->arch.fpu_ctxt, ctxt.fpu_regs, sizeof(ctxt.fpu_regs));
+ /* In case xsave-absent save file is restored on a xsave-capable host */
+ if ( cpu_has_xsave && !xsave_enabled(v) )
+ {
+ struct xsave_struct *xsave_area = v->arch.xsave_area;
- memcpy(v->arch.xsave_area, ctxt.fpu_regs, sizeof(ctxt.fpu_regs));
- xsave_area->xsave_hdr.xstate_bv = XSTATE_FP_SSE;
- if ( cpu_has_xsaves || cpu_has_xsavec )
- xsave_area->xsave_hdr.xcomp_bv = XSTATE_FP_SSE |
- XSTATE_COMPACTION_ENABLED;
+ xsave_area->xsave_hdr.xstate_bv = XSTATE_FP_SSE;
+ if ( cpu_has_xsaves || cpu_has_xsavec )
+ xsave_area->xsave_hdr.xcomp_bv = XSTATE_FP_SSE |
+ XSTATE_COMPACTION_ENABLED;
+ }
}
- else
- memcpy(v->arch.fpu_ctxt, ctxt.fpu_regs, sizeof(ctxt.fpu_regs));
v->arch.user_regs.eax = ctxt.rax;
v->arch.user_regs.ebx = ctxt.rbx;
@@ -2127,7 +2142,6 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
v->arch.debugreg[7] = ctxt.dr7;
v->arch.vgc_flags = VGCF_online;
- v->fpu_initialised = 1;
/* Auxiliary processors should be woken immediately. */
v->is_initialised = 1;
diff --git a/xen/include/public/arch-x86/hvm/save.h b/xen/include/public/arch-x86/hvm/save.h
index 29d513c..b6b1bf8 100644
--- a/xen/include/public/arch-x86/hvm/save.h
+++ b/xen/include/public/arch-x86/hvm/save.h
@@ -47,7 +47,9 @@ DECLARE_HVM_SAVE_TYPE(HEADER, 1, struct hvm_save_header);
/*
* Processor
*
- * Compat: Pre-3.4 didn't have msr_tsc_aux
+ * Compat:
+ * - Pre-3.4 didn't have msr_tsc_aux
+ * - Pre-4.7 didn't have fpu_initialised
*/
struct hvm_hw_cpu {
@@ -157,6 +159,10 @@ struct hvm_hw_cpu {
};
/* error code for pending event */
uint32_t error_code;
+
+#define _XEN_X86_FPU_INITIALISED 0
+#define XEN_X86_FPU_INITIALISED (1U<<_XEN_X86_FPU_INITIALISED)
+ uint32_t flags;
};
struct hvm_hw_cpu_compat {
@@ -275,12 +281,19 @@ static inline int _hvm_hw_fix_cpu(void *h, uint32_t size) {
struct hvm_hw_cpu_compat cmp;
} *ucpu = (union hvm_hw_cpu_union *)h;
- /* If we copy from the end backwards, we should
- * be able to do the modification in-place */
- ucpu->nat.error_code = ucpu->cmp.error_code;
- ucpu->nat.pending_event = ucpu->cmp.pending_event;
- ucpu->nat.tsc = ucpu->cmp.tsc;
- ucpu->nat.msr_tsc_aux = 0;
+ if ( size == sizeof(struct hvm_hw_cpu_compat) )
+ {
+ /*
+ * If we copy from the end backwards, we should
+ * be able to do the modification in-place.
+ */
+ ucpu->nat.error_code = ucpu->cmp.error_code;
+ ucpu->nat.pending_event = ucpu->cmp.pending_event;
+ ucpu->nat.tsc = ucpu->cmp.tsc;
+ ucpu->nat.msr_tsc_aux = 0;
+ }
+ /* Mimic the old behaviour by unconditionally setting fpu_initialised. */
+ ucpu->nat.flags = XEN_X86_FPU_INITIALISED;
return 0;
}
--
1.9.5 (Apple Git-50.3)
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 2/2] Revert "libxc: create an initial FPU state for HVM guests"
2016-01-12 16:12 [PATCH v6 0/2] Introduce a flags field to HVM CPU context Roger Pau Monne
2016-01-12 16:12 ` [PATCH v6 1/2] xen/hvm: introduce a flags field in the CPU save record Roger Pau Monne
@ 2016-01-12 16:12 ` Roger Pau Monne
1 sibling, 0 replies; 6+ messages in thread
From: Roger Pau Monne @ 2016-01-12 16:12 UTC (permalink / raw)
To: xen-devel
Cc: Wei Liu, Ian Campbell, Stefano Stabellini, Andrew Cooper,
Ian Jackson, Jan Beulich, Roger Pau Monne
This reverts commit d64dbbcc7c9934a46126c59d78536235908377ad:
Xen always set the FPU as initialized when loading a HVM context, so libxc
has to provide a valid FPU context when setting the CPU registers.
This was a stop-gap measure in order to unblock OSSTest Windows 7 failures
while a proper fix for the HVM CPU save/restore is being worked on.
This can now be reverted because a proper fix is in place and we can signal
in the save record whether the FPU is initialized or not.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
---
tools/libxc/xc_dom_x86.c | 38 --------------------------------------
1 file changed, 38 deletions(-)
diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index b8d2904..b650762 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -987,27 +987,6 @@ static int vcpu_hvm(struct xc_dom_image *dom)
struct hvm_save_descriptor end_d;
HVM_SAVE_TYPE(END) end;
} bsp_ctx;
- /*
- * The layout of the fpu context structure is the same for
- * both 32 and 64 bits.
- */
- struct {
- uint16_t fcw;
- uint16_t fsw;
- uint8_t ftw;
- uint8_t rsvd1;
- uint16_t fop;
- union {
- uint64_t addr;
- struct {
- uint32_t offs;
- uint16_t sel;
- uint16_t rsvd;
- };
- } fip, fdp;
- uint32_t mxcsr;
- uint32_t mxcsr_mask;
- } *fpu_ctxt;
uint8_t *full_ctx = NULL;
int rc;
@@ -1075,23 +1054,6 @@ static int vcpu_hvm(struct xc_dom_image *dom)
/* Set the control registers. */
bsp_ctx.cpu.cr0 = X86_CR0_PE | X86_CR0_ET;
- /*
- * XXX: Set initial FPU state.
- *
- * This should be removed once Xen is able to know if the
- * FPU state saved is valid or not, now Xen always sets
- * fpu_initialised to true regardless of the FPU state.
- *
- * The code below mimics the FPU sate after executing
- * fninit
- * ldmxcsr 0x1f80
- */
- fpu_ctxt = (typeof(fpu_ctxt))bsp_ctx.cpu.fpu_regs;
-
- fpu_ctxt->fcw = 0x37f;
- fpu_ctxt->ftw = 0xff;
- fpu_ctxt->mxcsr = 0x1f80;
-
/* Set the IP. */
bsp_ctx.cpu.rip = dom->parms.phys_entry;
--
1.9.5 (Apple Git-50.3)
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^ permalink raw reply related [flat|nested] 6+ messages in thread