Re: [Xen-devel] [PATCH] x86/boot: Don't explicitly map the VGA region as UC-

2019-09-06 Thread Jan Beulich
On 05.09.2019 21:04, Andrew Cooper wrote: > All 64-bit capable processors use PAT, and with PAT, it is explicitly > permitted to have mappings with a cacheability different to MTRRs. > > On a native system with a real legacy VGA region, MTRRs will cause the region > to be UC-. Minor correction: M

Re: [Xen-devel] [PATCH] x86/boot: Don't explicitly map the VGA region as UC-

2019-09-06 Thread Andrew Cooper
On 06/09/2019 12:06, Roger Pau Monné wrote: > On Thu, Sep 05, 2019 at 08:04:18PM +0100, Andrew Cooper wrote: >> All 64-bit capable processors use PAT, and with PAT, it is explicitly >> permitted to have mappings with a cacheability different to MTRRs. >> >> On a native system with a real legacy VGA

Re: [Xen-devel] [PATCH] x86/boot: Don't explicitly map the VGA region as UC-

2019-09-06 Thread Roger Pau Monné
On Thu, Sep 05, 2019 at 08:04:18PM +0100, Andrew Cooper wrote: > All 64-bit capable processors use PAT, and with PAT, it is explicitly > permitted to have mappings with a cacheability different to MTRRs. > > On a native system with a real legacy VGA region, MTRRs will cause the region > to be UC-.

[Xen-devel] [PATCH] x86/boot: Don't explicitly map the VGA region as UC-

2019-09-05 Thread Andrew Cooper
All 64-bit capable processors use PAT, and with PAT, it is explicitly permitted to have mappings with a cacheability different to MTRRs. On a native system with a real legacy VGA region, MTRRs will cause the region to be UC-. When booting virtualised, this range may be RAM and not a legacy VGA re