| Message ID | 1579097798-106243-1-git-send-email-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 6849b5eba1965ceb0cad3a75877ef4569dd3638e |
| Headers | show |
| Series | ARM: virt: Relax arch timer version check during early boot | expand |
+ Marc + kvmarm@lists.cs.columbia.edu On 1/15/20 2:16 PM, Vladimir Murzin wrote: > Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to > have values other than 0 or 1. At the moment, Linux is quite strict in > the way it handles this field at early boot and will not configure > arch timer if it doesn't find the value 1. > > Since here use ubfx for arch timer version extraction (hyb-stub build > with -march=armv7-a, so it is safe) > > To help backports (even though the code was correct at the time of writing) > Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to physical timers") > Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> > --- > arch/arm/kernel/hyp-stub.S | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S > index ae50203..6607fa8 100644 > --- a/arch/arm/kernel/hyp-stub.S > +++ b/arch/arm/kernel/hyp-stub.S > @@ -146,10 +146,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE > #if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER) > @ make CNTP_* and CNTPCT accessible from PL1 > mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1 > - lsr r7, #16 > - and r7, #0xf > - cmp r7, #1 > - bne 1f > + ubfx r7, r7, #16, #4 > + teq r7, #0 > + beq 1f > mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL > orr r7, r7, #3 @ PL1PCEN | PL1PCTEN > mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL >
Hi Vladimir, On 2020-01-20 11:46, Vladimir Murzin wrote: > + Marc > + kvmarm@lists.cs.columbia.edu > > On 1/15/20 2:16 PM, Vladimir Murzin wrote: >> Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to >> have values other than 0 or 1. At the moment, Linux is quite strict in >> the way it handles this field at early boot and will not configure >> arch timer if it doesn't find the value 1. >> >> Since here use ubfx for arch timer version extraction (hyb-stub build >> with -march=armv7-a, so it is safe) >> >> To help backports (even though the code was correct at the time of >> writing) >> Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to >> physical timers") >> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> I'm not opposed to such a change, but it'd be good to document what other values are expected here, as the current (Rev E_a) ARM ARM only mentions values 0 and 1. Thanks, M. >> --- >> arch/arm/kernel/hyp-stub.S | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S >> index ae50203..6607fa8 100644 >> --- a/arch/arm/kernel/hyp-stub.S >> +++ b/arch/arm/kernel/hyp-stub.S >> @@ -146,10 +146,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE >> #if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER) >> @ make CNTP_* and CNTPCT accessible from PL1 >> mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1 >> - lsr r7, #16 >> - and r7, #0xf >> - cmp r7, #1 >> - bne 1f >> + ubfx r7, r7, #16, #4 >> + teq r7, #0 >> + beq 1f >> mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL >> orr r7, r7, #3 @ PL1PCEN | PL1PCTEN >> mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL >>
Hi Marc, On 1/20/20 11:14 AM, Marc Zyngier wrote: > Hi Vladimir, > > On 2020-01-20 11:46, Vladimir Murzin wrote: >> + Marc >> + kvmarm@lists.cs.columbia.edu >> >> On 1/15/20 2:16 PM, Vladimir Murzin wrote: >>> Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to >>> have values other than 0 or 1. At the moment, Linux is quite strict in >>> the way it handles this field at early boot and will not configure >>> arch timer if it doesn't find the value 1. >>> >>> Since here use ubfx for arch timer version extraction (hyb-stub build >>> with -march=armv7-a, so it is safe) >>> >>> To help backports (even though the code was correct at the time of writing) >>> Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to physical timers") >>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> > > I'm not opposed to such a change, but it'd be good to document what other values > are expected here, as the current (Rev E_a) ARM ARM only mentions values 0 and 1. That true, ARM ARM doesn't mention it yet. OTOH, should we really care about exact values as soon it stays compatible? Cheers Vladimir > > Thanks, > > M. > >>> --- >>> arch/arm/kernel/hyp-stub.S | 7 +++---- >>> 1 file changed, 3 insertions(+), 4 deletions(-) >>> >>> diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S >>> index ae50203..6607fa8 100644 >>> --- a/arch/arm/kernel/hyp-stub.S >>> +++ b/arch/arm/kernel/hyp-stub.S >>> @@ -146,10 +146,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE >>> #if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER) >>> @ make CNTP_* and CNTPCT accessible from PL1 >>> mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1 >>> - lsr r7, #16 >>> - and r7, #0xf >>> - cmp r7, #1 >>> - bne 1f >>> + ubfx r7, r7, #16, #4 >>> + teq r7, #0 >>> + beq 1f >>> mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL >>> orr r7, r7, #3 @ PL1PCEN | PL1PCTEN >>> mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL >>> >
On 2020-01-20 12:34, Vladimir Murzin wrote: > Hi Marc, > > On 1/20/20 11:14 AM, Marc Zyngier wrote: >> Hi Vladimir, >> >> On 2020-01-20 11:46, Vladimir Murzin wrote: >>> + Marc >>> + kvmarm@lists.cs.columbia.edu >>> >>> On 1/15/20 2:16 PM, Vladimir Murzin wrote: >>>> Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to >>>> have values other than 0 or 1. At the moment, Linux is quite strict >>>> in >>>> the way it handles this field at early boot and will not configure >>>> arch timer if it doesn't find the value 1. >>>> >>>> Since here use ubfx for arch timer version extraction (hyb-stub >>>> build >>>> with -march=armv7-a, so it is safe) >>>> >>>> To help backports (even though the code was correct at the time of >>>> writing) >>>> Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to >>>> physical timers") >>>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> >> >> I'm not opposed to such a change, but it'd be good to document what >> other values >> are expected here, as the current (Rev E_a) ARM ARM only mentions >> values 0 and 1. > > That true, ARM ARM doesn't mention it yet. OTOH, should we really care > about exact values as soon it stays compatible? That's for you to say, really. But given that you hint at some changes, it'd be good to have at least a short sentence explaining that, for example, "upcoming revisions of the architecture will allow different ID_PFR1.GenTimer values while preserving backward compatibility". Other than that, feel free to add my Acked-by: Marc Zyngier <maz@kernel.org> Thanks, M.
diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S index ae50203..6607fa8 100644 --- a/arch/arm/kernel/hyp-stub.S +++ b/arch/arm/kernel/hyp-stub.S @@ -146,10 +146,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE #if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER) @ make CNTP_* and CNTPCT accessible from PL1 mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1 - lsr r7, #16 - and r7, #0xf - cmp r7, #1 - bne 1f + ubfx r7, r7, #16, #4 + teq r7, #0 + beq 1f mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL orr r7, r7, #3 @ PL1PCEN | PL1PCTEN mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL
Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to have values other than 0 or 1. At the moment, Linux is quite strict in the way it handles this field at early boot and will not configure arch timer if it doesn't find the value 1. Since here use ubfx for arch timer version extraction (hyb-stub build with -march=armv7-a, so it is safe) To help backports (even though the code was correct at the time of writing) Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to physical timers") Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> --- arch/arm/kernel/hyp-stub.S | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)