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Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache informatio
From: |
Moger, Babu |
Subject: |
Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently |
Date: |
Mon, 7 May 2018 21:14:27 +0000 |
Eduardo,
Thanks for all the comments. Will respond to each one separately.
> -----Original Message-----
> From: Eduardo Habkost [mailto:address@hidden
> Sent: Monday, May 7, 2018 2:05 PM
> To: Moger, Babu <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden
> Subject: Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache
> information consistently
>
> Hi,
>
> I was about to apply this because I assumed it was the same patch
> I sent in March, but then I found this:
>
> On Thu, Apr 26, 2018 at 11:26:41AM -0500, Babu Moger wrote:
> > From: Eduardo Habkost <address@hidden>
> >
> > Instead of having a collection of macros that need to be used in
> > complex expressions to build CPUID data, define a CPUCacheInfo
> > struct that can hold information about a given cache. Helper
> > functions will take a CPUCacheInfo struct as input to encode
> > CPUID leaves for a cache.
> >
> > This will help us ensure consistency between cache information
> > CPUID leaves, and make the existing inconsistencies in CPUID info
> > more visible.
> >
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > Signed-off-by: Babu Moger <address@hidden>
> > Tested-by: Geoffrey McRae <address@hidden>
> [...]
> > -#define L2_ASSOCIATIVITY 16
> [...]
> > /*FIXME: CPUID leaf 0x80000006 is inconsistent with leaves 2 & 4 */
> > +static CPUCacheInfo l2_cache_amd = {
> [...]
> > + .associativity = 8,
> [...]
> > +};
> [...]
> > case 0x80000006:
> [...]
> > - *ecx = (L2_SIZE_KB_AMD << 16) | \
> > - (AMD_ENC_ASSOC(L2_ASSOCIATIVITY) << 12) | \
> > - (L2_LINES_PER_TAG << 8) | (L2_LINE_SIZE);
> [...]
> > + encode_cache_cpuid80000006(&l2_cache_amd,
> > + cpu->enable_l3_cache ? &l3_cache : NULL,
> > + ecx, edx);
> [...]
>
> The structs added by this patch are supposed to represent the
> legacy cache sizes, and must match the old code. My original
> patch set l2_cache_amd.associativity=16 because of that.
>
> This patch changes 0x80000006 from associativity=16 to
> associativity=8. Why?
The original code had a bug here. The associativity should have been 8.
My earlier response from the thread
http://patchwork.ozlabs.org/patch/884880/
This should have been 8-way. This is a bug. Will fix.
This should have been (AMD_ENC_ASSOC(L2_ASSOCIATIVITY_AMD) << 12)
>
> --
> Eduardo
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Eduardo Habkost, 2018/05/07
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently,
Moger, Babu <=
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Eduardo Habkost, 2018/05/07
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Moger, Babu, 2018/05/07
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Moger, Babu, 2018/05/08
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Eduardo Habkost, 2018/05/08
- Re: [Qemu-devel] [PATCH v7 1/9] i386: Helpers to encode cache information consistently, Moger, Babu, 2018/05/08