> -----Original Message----- > From: Michael Kelley (LINUX) <mikelley@xxxxxxxxxxxxx> > Sent: Saturday, May 20, 2023 10:20 PM > To: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>; tglx@xxxxxxxxxxxxx; > mingo@xxxxxxxxxx; bp@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx; > x86@xxxxxxxxxx; hpa@xxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; > Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui > <decui@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux- > hyperv@xxxxxxxxxxxxxxx > Cc: Saurabh Singh Sengar <ssengar@xxxxxxxxxxxxx> > Subject: [EXTERNAL] RE: [PATCH 2/2] Drivers: hv: Kconfig: Add > HYPERV_VTL_MODE dependencies > > From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> > > > > MTRRs are not per-VTL and are controlled by VTL0, make sure it is > > disabled for all other VTLs. > > Clarifying the wording a bit: > > MTRRs are not per-VTL, but are always controlled by VTL0. Allow > building for VTLs other than VTL0 only when MTRR functionality is disabled. Ok > > > > > X86_MPPARSE scans low memory for MP tables, which is not required for > > Hyper-V VTL platforms. > > Is the above statement saying that MP tables aren't required, so remove the > code to save space? Or is there a problem/failure if MP table code > runs and scans low memory? *Requiring* that it be disabled, and the > reference to scanning low memory makes me think it might be the latter, in > which case I'd suggest this more forceful wording: > > The MP table code scans low memory, which causes failures in VTLs > other than VTL0. Allow building for VTLs other than VTL0 only when > MP table functionality is disabled. Ok > > If you can give slightly more detail about "causes failures" (a panic? > some other problem?) that would be good too. When CONFIG_X86_MPPARSE is enabled, the kernel will scan low memory, looking for MP tables. In Hyper-V VBS setup, lower memory is assigned to VTL0. This lower memory may contain the actual MPPARSE table for VTL0, which can confuse the VTLx kernel and cause issues. (x > 0) > > Michael > > > > > Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> > > --- > > drivers/hv/Kconfig | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig index > > 00242107d62e..c8d443886b9d 100644 > > --- a/drivers/hv/Kconfig > > +++ b/drivers/hv/Kconfig > > @@ -16,6 +16,8 @@ config HYPERV > > config HYPERV_VTL_MODE > > bool "Enable Linux to boot in VTL context" > > depends on X86_64 && HYPERV > > + depends on !MTRR > > + depends on !X86_MPPARSE > > default n > > help > > Virtual Secure Mode (VSM) is a set of hypervisor capabilities and > > -- > > 2.34.1
