[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 3/4] xen/hvm: introduce a fpu_uninitialised field to the CPU save record
El 20/11/15 a les 16.49, Jan Beulich ha escrit: >>>> On 18.11.15 at 17:37, <roger.pau@xxxxxxxxxx> wrote: >> @@ -2091,7 +2092,8 @@ static int hvm_load_cpu_ctxt(struct domain *d, >> hvm_domain_context_t *h) >> 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; >> + xsave_area->xsave_hdr.xstate_bv = ctxt.fpu_initialised ? >> + XSTATE_FP_SSE : 0; >> } >> else >> memcpy(v->arch.fpu_ctxt, ctxt.fpu_regs, sizeof(ctxt.fpu_regs)); > > Question is - are the memcpy()s here really meaningful/valid > when !ctxt.fpu_initialized? I.e. shouldn't this code rather be > skipped instead of getting modified? If !fpu_initialized the fpu context save record is all zeroed out. I don't think it matters much (apart from saving a few CPU cycles). I can send a new version that doesn't save/restore the fpu context at all if !fpu_initialised. >> @@ -157,6 +159,8 @@ struct hvm_hw_cpu { >> }; >> /* error code for pending event */ >> uint32_t error_code; >> + /* is fpu initialised? */ >> + uint32_t fpu_initialised; > > A whole uint32_t for just one bit? Didn't we talk about making this > new field a flags one, consuming just one bit from it? AFAIK we agreed on adding this field to the tail and making it a uint32_t so that when new fields are added they can be detected by looking at the size of the structure: http://marc.info/?l=xen-devel&m=144490321208291 >> @@ -266,6 +270,7 @@ struct hvm_hw_cpu_compat { >> }; >> /* error code for pending event */ >> uint32_t error_code; >> + /*uint32_t fpu_initialised; COMPAT */ >> }; > > I think this is misleading - the compat structure never has this field. Right, I will remove it. Roger. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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