On 12/09/18 09:29, Sergey Dyasli wrote:
> On Tue, 2018-09-11 at 19:56 +0100, Andrew Cooper wrote:
>> Rename them to guest_{rd,wr}msr_xen() for consistency, and because the _regs
>> suffix isn't very appropriate.
>>
>> Update them to take a vcpu pointer rather than presuming that they act on
>> current, and switch to using X86EMUL_* return values.
>>
>> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
>> ---
>> CC: Jan Beulich <jbeul...@suse.com>
>> CC: Wei Liu <wei.l...@citrix.com>
>> CC: Roger Pau Monné <roger....@citrix.com>
>> CC: Sergey Dyasli <sergey.dya...@citrix.com>
>>
>> v3:
>> * Clean up after splitting the series.
>> ---
>> xen/arch/x86/msr.c | 6 ++----
>> xen/arch/x86/traps.c | 29 +++++++++++++----------------
>> xen/include/asm-x86/processor.h | 4 ++--
>> 3 files changed, 17 insertions(+), 22 deletions(-)
>>
>> diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
>> index cf0dc27..8f02a89 100644
>> --- a/xen/arch/x86/msr.c
>> +++ b/xen/arch/x86/msr.c
>> @@ -156,8 +156,7 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr,
>> uint64_t *val)
>>
>> /* Fallthrough. */
>> case 0x40000200 ... 0x400002ff:
>> - ret = (rdmsr_hypervisor_regs(msr, val)
>> - ? X86EMUL_OKAY : X86EMUL_EXCEPTION);
>> + ret = guest_rdmsr_xen(v, msr, val);
>> break;
>>
>> default:
>> @@ -277,8 +276,7 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t
>> val)
>>
>> /* Fallthrough. */
>> case 0x40000200 ... 0x400002ff:
>> - ret = (wrmsr_hypervisor_regs(msr, val) == 1
>> - ? X86EMUL_OKAY : X86EMUL_EXCEPTION);
>> + ret = guest_wrmsr_xen(v, msr, val);
>> break;
>>
>> default:
>> diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
>> index 7c17806..3988753 100644
>> --- a/xen/arch/x86/traps.c
>> +++ b/xen/arch/x86/traps.c
>> @@ -768,29 +768,25 @@ static void do_trap(struct cpu_user_regs *regs)
>> trapnr, trapstr(trapnr), regs->error_code);
>> }
>>
>> -/* Returns 0 if not handled, and non-0 for success. */
>> -int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val)
>> +int guest_rdmsr_xen(const struct vcpu *v, uint32_t idx, uint64_t *val)
>> {
>> - struct domain *d = current->domain;
>> + const struct domain *d = v->domain;
>> /* Optionally shift out of the way of Viridian architectural MSRs. */
>> uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
>>
>> switch ( idx - base )
>> {
>> case 0: /* Write hypercall page MSR. Read as zero. */
>> - {
>> *val = 0;
>> - return 1;
>> - }
>> + return X86EMUL_OKAY;
>> }
>>
>> - return 0;
>> + return X86EMUL_EXCEPTION;
>> }
>>
>> -/* Returns 1 if handled, 0 if not and -Exx for error. */
>> -int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
>> +int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val)
>> {
>> - struct domain *d = current->domain;
>> + struct domain *d = v->domain;
>> /* Optionally shift out of the way of Viridian architectural MSRs. */
>> uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
>>
>> @@ -809,7 +805,7 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
>> gdprintk(XENLOG_WARNING,
>> "wrmsr hypercall page index %#x unsupported\n",
>> page_index);
>> - return 0;
>> + return X86EMUL_EXCEPTION;
>> }
>>
>> page = get_page_from_gfn(d, gmfn, &t, P2M_ALLOC);
>> @@ -822,13 +818,13 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
>> if ( p2m_is_paging(t) )
>> {
>> p2m_mem_paging_populate(d, gmfn);
>> - return -ERESTART;
>> + return X86EMUL_RETRY;
> Previously -ERESTART would've been converted to X86EMUL_EXCEPTION. But
> with this patch, X86EMUL_RETRY will actually be returned. I don't think
> that callers can handle this situation.
>
> E.g. the code from vmx_vmexit_handler():
>
> case EXIT_REASON_MSR_WRITE:
> switch ( hvm_msr_write_intercept(regs->ecx, msr_fold(regs), 1) )
> {
> case X86EMUL_OKAY:
> update_guest_eip(); /* Safe: WRMSR */
> break;
>
> case X86EMUL_EXCEPTION:
> hvm_inject_hw_exception(TRAP_gp_fault, 0);
> break;
> }
> break;
Hmm lovely, so it was broken before, but should be correct now.
RETRY has caused an entry to go onto the paging ring, which will pause
the vcpu until a reply occurs, after which we will re-enter the guest
without having moved RIP forwards, re-execute the wrmsr instruction, and
this time succeed because the frame has been paged in.
~Andrew
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
