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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1728905196; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3nrZRX6TfU/x+EEfp90rIVyosRBuV8WxY4dYQBhPLrg=; b=DaUzOAxHOATqjR0StA+MJZ/8E4Kq8a633jNdFGl5ZByu+G50L6ZyZF+dkeUPwX5VTyIzfm zzYpWn0z3L0Ypzh4g5lRkvhXojy4YPuS/5Fcx3O6AeS8iydPlrDT5CkHsbk6fThBA6K4ul Afv3tKcqEahZ7FhsrHCzlu6tjcGE42Q= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3BC401424; Mon, 14 Oct 2024 04:29:00 -0700 (PDT) Received: from [10.57.86.130] (unknown [10.57.86.130]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1A9D33F51B; Mon, 14 Oct 2024 04:28:27 -0700 (PDT) Message-ID: Date: Mon, 14 Oct 2024 12:28:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 55/57] arm64: TRAMP_VALIAS is no longer compile-time constant Content-Language: en-GB To: Ard Biesheuvel Cc: Andrew Morton , Anshuman Khandual , Catalin Marinas , David Hildenbrand , Greg Marsden , Ivan Ivanov , Kalesh Singh , Marc Zyngier , Mark Rutland , Matthias Brugger , Miroslav Benes , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20241014105514.3206191-1-ryan.roberts@arm.com> <20241014105912.3207374-1-ryan.roberts@arm.com> <20241014105912.3207374-55-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2511A40012 X-Stat-Signature: 87pmezdsobxofdmd7faf8hnrnidpfh3w X-Rspam-User: X-HE-Tag: 1728905305-715125 X-HE-Meta: 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 VCxPlvpC ThSvZmnB33iTabQF0ZGkrlf2UZx2inOloLBa5QloKgrAJgDsYw9YKu5oYUwaJe9KouM4PjccoCAF7y5Q6E0/V2Pchbb5zvHF4E7s/kcWJnHH46k94uZzAEyy9FHxU103oGaT0hKsxSL1FjnQnxUC3kzZuq3SUmvtJ+lWna08Z9OPmraU/pUW3scfflS7eooU7e9y7fXsk1OBZwBN1pW9nxxyCNlX0jTgHyhnuB7Ccx762Nn8rUbpm05n0AKLoM5T/ubwDLDR/DvYxcjPNW4C5TQ8LuA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 14/10/2024 12:21, Ard Biesheuvel wrote: > Hi Ryan, > > On Mon, 14 Oct 2024 at 13:02, Ryan Roberts wrote: >> >> When boot-time page size is in operation, TRAMP_VALIAS is no longer a >> compile-time constant, because the VA of a fixmap slot depends upon >> PAGE_SIZE. >> >> Let's handle this by instead exporting the slot index, >> FIX_ENTRY_TRAMP_BEGIN,to assembly, then do the TRAMP_VALIAS calculation >> per page size and use alternatives to decide which variant to activate. >> >> Note that for the tramp_map_kernel case, we are one instruction short of >> space in the vector to have NOPs for all 3 page size variants. So we do >> if/else for 16K/64K and branch around it for the 4K case. This saves 2 >> instructions. >> >> Signed-off-by: Ryan Roberts >> --- >> >> ***NOTE*** >> Any confused maintainers may want to read the cover note here for context: >> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/ >> >> arch/arm64/kernel/asm-offsets.c | 2 +- >> arch/arm64/kernel/entry.S | 50 ++++++++++++++++++++++++++------- >> 2 files changed, 41 insertions(+), 11 deletions(-) >> >> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c >> index f32b8d7f00b2a..c45fa3e281884 100644 >> --- a/arch/arm64/kernel/asm-offsets.c >> +++ b/arch/arm64/kernel/asm-offsets.c >> @@ -172,7 +172,7 @@ int main(void) >> DEFINE(ARM64_FTR_SYSVAL, offsetof(struct arm64_ftr_reg, sys_val)); >> BLANK(); >> #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 >> - DEFINE(TRAMP_VALIAS, TRAMP_VALIAS); >> + DEFINE(FIX_ENTRY_TRAMP_BEGIN, FIX_ENTRY_TRAMP_BEGIN); >> #endif >> #ifdef CONFIG_ARM_SDE_INTERFACE >> DEFINE(SDEI_EVENT_INTREGS, offsetof(struct sdei_registered_event, interrupted_regs)); >> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S >> index 7ef0e127b149f..ba47dc8672c04 100644 >> --- a/arch/arm64/kernel/entry.S >> +++ b/arch/arm64/kernel/entry.S >> @@ -101,11 +101,27 @@ >> .org .Lventry_start\@ + 128 // Did we overflow the ventry slot? >> .endm >> >> +#define TRAMP_VALIAS(page_shift) (FIXADDR_TOP - (FIX_ENTRY_TRAMP_BEGIN << (page_shift))) >> + >> .macro tramp_alias, dst, sym >> - .set .Lalias\@, TRAMP_VALIAS + \sym - .entry.tramp.text >> - movz \dst, :abs_g2_s:.Lalias\@ >> - movk \dst, :abs_g1_nc:.Lalias\@ >> - movk \dst, :abs_g0_nc:.Lalias\@ >> +alternative_if ARM64_USE_PAGE_SIZE_4K >> + .set .Lalias4k\@, TRAMP_VALIAS(ARM64_PAGE_SHIFT_4K) + \sym - .entry.tramp.text >> + movz \dst, :abs_g2_s:.Lalias4k\@ >> + movk \dst, :abs_g1_nc:.Lalias4k\@ >> + movk \dst, :abs_g0_nc:.Lalias4k\@ >> +alternative_else_nop_endif >> +alternative_if ARM64_USE_PAGE_SIZE_16K >> + .set .Lalias16k\@, TRAMP_VALIAS(ARM64_PAGE_SHIFT_16K) + \sym - .entry.tramp.text >> + movz \dst, :abs_g2_s:.Lalias16k\@ >> + movk \dst, :abs_g1_nc:.Lalias16k\@ >> + movk \dst, :abs_g0_nc:.Lalias16k\@ >> +alternative_else_nop_endif >> +alternative_if ARM64_USE_PAGE_SIZE_64K >> + .set .Lalias64k\@, TRAMP_VALIAS(ARM64_PAGE_SHIFT_64K) + \sym - .entry.tramp.text >> + movz \dst, :abs_g2_s:.Lalias64k\@ >> + movk \dst, :abs_g1_nc:.Lalias64k\@ >> + movk \dst, :abs_g0_nc:.Lalias64k\@ >> +alternative_else_nop_endif > > Since you're changing these, might as well drop the middle movk as the > fixmap is now always in the top 2 GiB of the VA space. > > However, wouldn't it be better to reuse the existing callback > alternative stuff that Marc added for KVM? Yes, I agree. Mark suggested the same thing when we were talking the other day too. I'll definitely use the callbacks for next version, but I didn't want to hold up the RFC any further - I'd already spent way too much time polishing. > > Same applies below, I reckon. > >> .endm >> >> /* >> @@ -627,16 +643,30 @@ SYM_CODE_END(ret_to_user) >> bic \tmp, \tmp, #USER_ASID_FLAG >> msr ttbr1_el1, \tmp >> #ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003 >> -alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003 >> +alternative_if_not ARM64_WORKAROUND_QCOM_FALKOR_E1003 >> + b .Lskip_falkor_e1003\@ >> +alternative_else_nop_endif >> /* ASID already in \tmp[63:48] */ >> - movk \tmp, #:abs_g2_nc:(TRAMP_VALIAS >> 12) >> - movk \tmp, #:abs_g1_nc:(TRAMP_VALIAS >> 12) >> - /* 2MB boundary containing the vectors, so we nobble the walk cache */ >> - movk \tmp, #:abs_g0_nc:((TRAMP_VALIAS & ~(SZ_2M - 1)) >> 12) >> +alternative_if ARM64_USE_PAGE_SIZE_4K >> + movk \tmp, #:abs_g2_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_4K) >> 12) >> + movk \tmp, #:abs_g1_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_4K) >> 12) >> + movk \tmp, #:abs_g0_nc:((TRAMP_VALIAS(ARM64_PAGE_SHIFT_4K) & ~(SZ_2M - 1)) >> 12) >> + b .Lfinish_falkor_e1003\@ >> +alternative_else_nop_endif >> +alternative_if ARM64_USE_PAGE_SIZE_16K >> + movk \tmp, #:abs_g2_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_16K) >> 12) >> + movk \tmp, #:abs_g1_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_16K) >> 12) >> + movk \tmp, #:abs_g0_nc:((TRAMP_VALIAS(ARM64_PAGE_SHIFT_16K) & ~(SZ_2M - 1)) >> 12) >> +alternative_else /* ARM64_USE_PAGE_SIZE_64K */ >> + movk \tmp, #:abs_g2_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_64K) >> 12) >> + movk \tmp, #:abs_g1_nc:(TRAMP_VALIAS(ARM64_PAGE_SHIFT_64K) >> 12) >> + movk \tmp, #:abs_g0_nc:((TRAMP_VALIAS(ARM64_PAGE_SHIFT_64K) & ~(SZ_2M - 1)) >> 12) >> +alternative_endif >> +.Lfinish_falkor_e1003\@: >> isb >> tlbi vae1, \tmp >> dsb nsh >> -alternative_else_nop_endif >> +.Lskip_falkor_e1003\@: >> #endif /* CONFIG_QCOM_FALKOR_ERRATUM_1003 */ >> .endm >> >> -- >> 2.43.0 >>