[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Pranavkumar Sawargaonkar]

X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.

This can happen on any ARM/ARM64 board running bootloader in
Hyp-mode (or EL2-mode) with MMU enabled.

This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.

Changelog:

V2:
 - Flush Hyp-mode TLBs for both KVM ARM32 and KVM ARM64 at boot time

V1:
 - Initial patch with only arm64 change

Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Anup Patel <anup.patel@linaro.org>
---
 arch/arm/kvm/init.S       |    4 ++++
 arch/arm64/kvm/hyp-init.S |    4 ++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index 1b9844d..ee4f744 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S
@@ -98,6 +98,10 @@ __do_hyp_init:
 	mrc	p15, 0, r0, c10, c2, 1
 	mcr	p15, 4, r0, c10, c2, 1
 
+	@ Invalidate the stale TLBs from Bootloader
+	mcr	p15, 4, r0, c8, c7, 0	@ TLBIALLH
+	dsb	ish
+
 	@ Set the HSCTLR to:
 	@  - ARM/THUMB exceptions: Kernel config (Thumb-2 kernel)
 	@  - Endianness: Kernel config
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index d968796..c319116 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -80,6 +80,10 @@ __do_hyp_init:
 	msr	mair_el2, x4
 	isb
 
+	/* Invalidate the stale TLBs from Bootloader */
+	tlbi	alle2
+	dsb	sy
+
 	mrs	x4, sctlr_el2
 	and	x4, x4, #SCTLR_EL2_EE	// preserve endianness of EL2
 	ldr	x5, =SCTLR_EL2_FLAGS
-- 
1.7.9.5

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Christoffer Dall]

On Thu, Jul 31, 2014 at 12:23:23PM +0530, Pranavkumar Sawargaonkar wrote:
> X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
> have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.
> 
> This can happen on any ARM/ARM64 board running bootloader in
> Hyp-mode (or EL2-mode) with MMU enabled.
> 
> This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
> on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.
> 
> Changelog:
> 
> V2:
>  - Flush Hyp-mode TLBs for both KVM ARM32 and KVM ARM64 at boot time
> 
> V1:
>  - Initial patch with only arm64 change
> 
> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
> Signed-off-by: Anup Patel <anup.patel@linaro.org>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Marc Zyngier]

Hi Pranav,

On Thu, Jul 31 2014 at  7:53:23 am BST, Pranavkumar Sawargaonkar <pranavkumar@linaro.org> wrote:
> X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
> have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.
>
> This can happen on any ARM/ARM64 board running bootloader in
> Hyp-mode (or EL2-mode) with MMU enabled.
>
> This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
> on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.
>
> Changelog:
>
> V2:
>  - Flush Hyp-mode TLBs for both KVM ARM32 and KVM ARM64 at boot time
>
> V1:
>  - Initial patch with only arm64 change
>
> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> ---
>  arch/arm/kvm/init.S       |    4 ++++
>  arch/arm64/kvm/hyp-init.S |    4 ++++
>  2 files changed, 8 insertions(+)
>
> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
> index 1b9844d..ee4f744 100644
> --- a/arch/arm/kvm/init.S
> +++ b/arch/arm/kvm/init.S
> @@ -98,6 +98,10 @@ __do_hyp_init:
>  	mrc	p15, 0, r0, c10, c2, 1
>  	mcr	p15, 4, r0, c10, c2, 1
>  
> +	@ Invalidate the stale TLBs from Bootloader
> +	mcr	p15, 4, r0, c8, c7, 0	@ TLBIALLH
> +	dsb	ish
> +
>  	@ Set the HSCTLR to:
>  	@  - ARM/THUMB exceptions: Kernel config (Thumb-2 kernel)
>  	@  - Endianness: Kernel config
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index d968796..c319116 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -80,6 +80,10 @@ __do_hyp_init:
>  	msr	mair_el2, x4
>  	isb
>  
> +	/* Invalidate the stale TLBs from Bootloader */
> +	tlbi	alle2
> +	dsb	sy
> +
>  	mrs	x4, sctlr_el2
>  	and	x4, x4, #SCTLR_EL2_EE	// preserve endianness of EL2
>  	ldr	x5, =SCTLR_EL2_FLAGS

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

	M.
-- 
Jazz is not dead. It just smells funny.

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Marc Zyngier]

On 04/08/14 13:06, Christoffer Dall wrote:
> On Thu, Jul 31, 2014 at 12:23:23PM +0530, Pranavkumar Sawargaonkar wrote:
>> X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
>> have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.
>>
>> This can happen on any ARM/ARM64 board running bootloader in
>> Hyp-mode (or EL2-mode) with MMU enabled.
>>
>> This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
>> on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.
>>
>> Changelog:
>>
>> V2:
>>  - Flush Hyp-mode TLBs for both KVM ARM32 and KVM ARM64 at boot time
>>
>> V1:
>>  - Initial patch with only arm64 change
>>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
>> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> 
> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

This should probably go in quickly as a fix.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Mark Rutland]

Hi Pranav,

On Thu, Jul 31, 2014 at 07:53:23AM +0100, Pranavkumar Sawargaonkar wrote:
> X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
> have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.

Nit: entries

> This can happen on any ARM/ARM64 board running bootloader in
> Hyp-mode (or EL2-mode) with MMU enabled.
> 
> This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
> on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.

I hit a similar issue intermittently on a Juno board when I boot Linux
as an EFI application, where CPU0 would get stuck in a recursive
exception at EL2 while initialising hyp. We don't nuke the TLBs in
efi_stub_entry nor do we do so in el2_setup, so there's the possibility
of stale EL2 TLB entries lying around from UEFI.

With this patch applied I'm unable to reproduce the issue (with ~30
boots so far). So:

Tested-by: Mark Rutland <mark.rutland@arm.com>

It would be nice to see this hit mainline soon.

Thanks,
Mark.

> 
> Changelog:
> 
> V2:
>  - Flush Hyp-mode TLBs for both KVM ARM32 and KVM ARM64 at boot time
> 
> V1:
>  - Initial patch with only arm64 change
> 
> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> ---
>  arch/arm/kvm/init.S       |    4 ++++
>  arch/arm64/kvm/hyp-init.S |    4 ++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
> index 1b9844d..ee4f744 100644
> --- a/arch/arm/kvm/init.S
> +++ b/arch/arm/kvm/init.S
> @@ -98,6 +98,10 @@ __do_hyp_init:
>  	mrc	p15, 0, r0, c10, c2, 1
>  	mcr	p15, 4, r0, c10, c2, 1
>  
> +	@ Invalidate the stale TLBs from Bootloader
> +	mcr	p15, 4, r0, c8, c7, 0	@ TLBIALLH
> +	dsb	ish
> +
>  	@ Set the HSCTLR to:
>  	@  - ARM/THUMB exceptions: Kernel config (Thumb-2 kernel)
>  	@  - Endianness: Kernel config
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index d968796..c319116 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -80,6 +80,10 @@ __do_hyp_init:
>  	msr	mair_el2, x4
>  	isb
>  
> +	/* Invalidate the stale TLBs from Bootloader */
> +	tlbi	alle2
> +	dsb	sy
> +
>  	mrs	x4, sctlr_el2
>  	and	x4, x4, #SCTLR_EL2_EE	// preserve endianness of EL2
>  	ldr	x5, =SCTLR_EL2_FLAGS
> -- 
> 1.7.9.5
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

[PATCH V2] ARM/ARM64: KVM: Nuke Hyp-mode tlbs before enabling MMU

[Marc Zyngier]

On 22/08/14 11:23, Mark Rutland wrote:
> Hi Pranav,
> 
> On Thu, Jul 31, 2014 at 07:53:23AM +0100, Pranavkumar Sawargaonkar wrote:
>> X-Gene u-boot runs in EL2 mode with MMU enabled hence we might
>> have stale EL2 tlb enteris when we enable EL2 MMU on each host CPU.
> 
> Nit: entries
> 
>> This can happen on any ARM/ARM64 board running bootloader in
>> Hyp-mode (or EL2-mode) with MMU enabled.
>>
>> This patch ensures that we flush all Hyp-mode (or EL2-mode) TLBs
>> on each host CPU before enabling Hyp-mode (or EL2-mode) MMU.
> 
> I hit a similar issue intermittently on a Juno board when I boot Linux
> as an EFI application, where CPU0 would get stuck in a recursive
> exception at EL2 while initialising hyp. We don't nuke the TLBs in
> efi_stub_entry nor do we do so in el2_setup, so there's the possibility
> of stale EL2 TLB entries lying around from UEFI.
> 
> With this patch applied I'm unable to reproduce the issue (with ~30
> boots so far). So:
> 
> Tested-by: Mark Rutland <mark.rutland@arm.com>
> 
> It would be nice to see this hit mainline soon.

Thanks for testing. I guess this is a candidate for stable as well.

	M.
-- 
Jazz is not dead. It just smells funny...