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From: Mark Rutland <mark.rutland@arm.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: maz@kernel.org, pbonzini@redhat.com,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	andre.przywara@arm.com
Subject: Re: [kvm-unit-tests RFC PATCH 04/16] arm/arm64: selftest: Add prefetch abort test
Date: Wed, 28 Aug 2019 15:09:25 +0100
Message-ID: <20190828140925.GC41023@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <1566999511-24916-5-git-send-email-alexandru.elisei@arm.com>

On Wed, Aug 28, 2019 at 02:38:19PM +0100, Alexandru Elisei wrote:
> When a guest tries to execute code from MMIO memory, KVM injects an
> external abort into that guest. We have now fixed the psci test to not
> fetch instructions from the I/O region, and it's not that often that a
> guest misbehaves in such a way. Let's expand our coverage by adding a
> proper test targetting this corner case.
> 
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> The fault injection path is broken for nested guests [1]. You can use the
> last patch from the thread [2] to successfully run the test at EL2.
> 
> [1] https://www.spinics.net/lists/arm-kernel/msg745391.html
> [2] https://www.spinics.net/lists/arm-kernel/msg750310.html
> 
>  lib/arm64/asm/esr.h |  3 ++
>  arm/selftest.c      | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 96 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/arm64/asm/esr.h b/lib/arm64/asm/esr.h
> index 8e5af4d90767..8c351631b0a0 100644
> --- a/lib/arm64/asm/esr.h
> +++ b/lib/arm64/asm/esr.h
> @@ -44,4 +44,7 @@
>  #define ESR_EL1_EC_BKPT32	(0x38)
>  #define ESR_EL1_EC_BRK64	(0x3C)
>  
> +#define ESR_EL1_FSC_MASK	(0x3F)
> +#define ESR_EL1_FSC_EXTABT	(0x10)
> +
>  #endif /* _ASMARM64_ESR_H_ */
> diff --git a/arm/selftest.c b/arm/selftest.c
> index 176231f32ee1..18cc0ad8f729 100644
> --- a/arm/selftest.c
> +++ b/arm/selftest.c
> @@ -16,6 +16,8 @@
>  #include <asm/psci.h>
>  #include <asm/smp.h>
>  #include <asm/barrier.h>
> +#include <asm/mmu.h>
> +#include <asm/pgtable.h>
>  
>  static void __user_psci_system_off(void)
>  {
> @@ -60,9 +62,38 @@ static void check_setup(int argc, char **argv)
>  		report_abort("missing input");
>  }
>  
> +extern pgd_t *mmu_idmap;
> +static void prep_io_exec(void)
> +{
> +	pgd_t *pgd = pgd_offset(mmu_idmap, 0);
> +	unsigned long sctlr;
> +
> +	/*
> +	 * AArch64 treats all regions writable at EL0 as PXN.

I didn't think that was the case, and I can't find wording to that
effect in the ARM ARM (looking at ARM DDI 0487E.a). Where is that
stated?

> Clear the user bit
> +	 * so we can execute code from the bottom I/O space (0G-1G) to simulate
> +	 * a misbehaved guest.
> +	 */
> +	pgd_val(*pgd) &= ~PMD_SECT_USER;
> +	flush_dcache_addr((unsigned long)pgd);

The virtualization extensions imply coherent page table walks, so I
don't think the cache maintenance is necessary (provided
TCR_EL1.{SH*,ORGN*,IRGN*} are configured appropriately.

> +	flush_tlb_page(0);
> +
> +	/* Make sure we can actually execute from a writable region */
> +#ifdef __arm__
> +	asm volatile("mrc p15, 0, %0, c1, c0, 0": "=r" (sctlr));
> +	sctlr &= ~CR_ST;
> +	asm volatile("mcr p15, 0, %0, c1, c0, 0" :: "r" (sctlr));
> +#else
> +	sctlr = read_sysreg(sctlr_el1);
> +	sctlr &= ~SCTLR_EL1_WXN;
> +	write_sysreg(sctlr, sctlr_el1);
> +#endif
> +	isb();
> +}

Thanks,
Mark.
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  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28 13:38 [kvm-unit-tests RFC PATCH 00/16] arm64: Run at EL2 Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 01/16] arm: selftest.c: Remove redundant check for Exception Level Alexandru Elisei
2019-08-28 14:32   ` Andrew Jones
2019-08-28 15:39     ` Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 02/16] arm/arm64: psci: Don't run C code without stack or vectors Alexandru Elisei
2019-08-28 14:45   ` Andrew Jones
2019-08-28 15:14     ` Alexandru Elisei
2019-09-02 14:55       ` Alexandru Elisei
2019-09-03  6:37         ` Andrew Jones
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 03/16] lib: arm/arm64: Add missing include for alloc_page.h in pgtable.h Alexandru Elisei
2019-08-28 14:47   ` Andrew Jones
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 04/16] arm/arm64: selftest: Add prefetch abort test Alexandru Elisei
2019-08-28 14:09   ` Mark Rutland [this message]
2019-08-29  8:18     ` Alexandru Elisei
2019-08-29 10:19       ` Mark Rutland
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 05/16] arm64: timer: Write to ICENABLER to disable timer IRQ Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 06/16] arm64: timer: EOIR the interrupt after masking the timer Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 07/16] arm64: timer: Test behavior when timer disabled or masked Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 08/16] lib: arm/arm64: Refuse to disable the MMU with non-identity stack pointer Alexandru Elisei
2019-08-28 14:55   ` Andrew Jones
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 09/16] lib: arm/arm64: Invalidate TLB before enabling MMU Alexandru Elisei
2019-08-28 14:59   ` Andrew Jones
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 10/16] lib: Add UL and ULL definitions to linux/const.h Alexandru Elisei
2019-08-28 15:10   ` Andrew Jones
2019-08-28 15:46     ` Alexandru Elisei
2019-08-28 16:19       ` Andrew Jones
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 11/16] lib: arm64: Run existing tests at EL2 Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 12/16] arm64: timer: Add test for EL2 timers Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 13/16] arm64: selftest: Add basic test for EL2 Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 14/16] lib: arm64: Add support for disabling and re-enabling VHE Alexandru Elisei
2019-08-28 14:19   ` Mark Rutland
2019-08-29  8:36     ` Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 15/16] arm64: selftest: Expand EL2 test to disable and re-enable VHE Alexandru Elisei
2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 16/16] arm64: timer: Run tests with VHE disabled Alexandru Elisei

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