From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6036915359C; Mon, 22 Apr 2024 16:15:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713802542; cv=none; b=NMzLErrf7zTYjc4VhWOaRH+D9HkgmQsqWKd7q96ZCbatJ4dvRvcWxryYmRUYiJTj176AM6SgRMS3sYFeB5oTlk79WYQ92HAnqeh+q5Qfl+PFO8uQfcO86N3dexeT5kClnkP1SKQqJCUcGn4VNqwG9yZ9/A9jFN9hYEFTd/7xKV0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713802542; c=relaxed/simple; bh=jynKJn+/06UQ5QBgTQSM/jEO3UnhaHdzA46/9F29Q2o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=irqRf4u15ku2LtgIAT6TBd4srOZdaEkEdPPv3SFM/+HN5i1ko8nE8rB5CbjG9pQ3udPaMNjyU7BURnMgRBVHeMsnicCYoC1r7gE0jVMbRQIT4QIwzFwvWYqrhMEq1cu4WvmxAWCwzA2ogyi4Undv93DleFUW3gcC6ATqz7pDaBk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 1BA5D339; Mon, 22 Apr 2024 09:16:08 -0700 (PDT) Received: from arm.com (e121798.cambridge.arm.com [10.1.197.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2466B3F7BD; Mon, 22 Apr 2024 09:15:38 -0700 (PDT) Date: Mon, 22 Apr 2024 17:15:35 +0100 From: Alexandru Elisei To: Suzuki K Poulose Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-arm-kernel@lists.infradead.org, maz@kernel.org, joey.gouly@arm.com, steven.price@arm.com, james.morse@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.com, andrew.jones@linux.dev, eric.auger@redhat.com Subject: Re: [kvm-unit-tests PATCH 08/33] arm: realm: Make uart available before MMU is enabled Message-ID: References: <20240412103408.2706058-1-suzuki.poulose@arm.com> <20240412103408.2706058-9-suzuki.poulose@arm.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi, On Mon, Apr 22, 2024 at 05:05:54PM +0100, Suzuki K Poulose wrote: > On 22/04/2024 16:38, Alexandru Elisei wrote: > > Hi, > > > > On Fri, Apr 12, 2024 at 11:33:43AM +0100, Suzuki K Poulose wrote: > > > From: Joey Gouly > > > > > > A Realm must access any emulated I/O mappings with the PTE_NS_SHARED bit set. > > > > What entity requires that a realm must access I/O mappings with the > > PTE_NS_SHARED bit set? Is that an architectural requirement? Or is it an > > implementation choice made by the VMM and/or KVM? > > RMM spec. An MMIO access in the Protected IPA must be emulated by Realm > world. If an MMIO access must be emulated by NS Host, it must be in the > Unprotected IPA. That's not exactly what I was asking. I was curious to know how a realm knows if a MMIO access is emulated by the Realm, and thus it must use a protected address, or it's emulated by the non-secure host, and it must use an unprotected address. Thanks, Alex > > Technically, a VMM could create a memory map, where the NS emulated I/O > are kept in the unprotected (upper) half. > > Or the VMM retains the current model and expects the Realm to use the > "Unprotected" alias. > > > Either way, applying the PTE_NS_SHARED attribute doesn't change anything and > works for both the models, as far as the Realm is concerned. > > > Suzuki > > > > > > > > Thanks, > > Alex > > > > > This is modelled as a PTE attribute, but is actually part of the address. > > > > > > So, when MMU is disabled, the "physical address" must reflect this bit set. We > > > access the UART early before the MMU is enabled. So, make sure the UART is > > > accessed always with the bit set. > > > > > > Signed-off-by: Joey Gouly > > > Signed-off-by: Suzuki K Poulose > > > --- > > > lib/arm/asm/pgtable.h | 5 +++++ > > > lib/arm/io.c | 24 +++++++++++++++++++++++- > > > lib/arm64/asm/pgtable.h | 5 +++++ > > > 3 files changed, 33 insertions(+), 1 deletion(-) > > > > > > diff --git a/lib/arm/asm/pgtable.h b/lib/arm/asm/pgtable.h > > > index 350039ff..7e85e7c6 100644 > > > --- a/lib/arm/asm/pgtable.h > > > +++ b/lib/arm/asm/pgtable.h > > > @@ -112,4 +112,9 @@ static inline pte_t *pte_alloc(pmd_t *pmd, unsigned long addr) > > > return pte_offset(pmd, addr); > > > } > > > +static inline unsigned long arm_shared_phys_alias(void *x) > > > +{ > > > + return ((unsigned long)(x) | PTE_NS_SHARED); > > > +} > > > + > > > #endif /* _ASMARM_PGTABLE_H_ */ > > > diff --git a/lib/arm/io.c b/lib/arm/io.c > > > index 836fa854..127727e4 100644 > > > --- a/lib/arm/io.c > > > +++ b/lib/arm/io.c > > > @@ -15,6 +15,8 @@ > > > #include > > > #include > > > #include > > > +#include > > > +#include > > > #include "io.h" > > > @@ -30,6 +32,24 @@ static struct spinlock uart_lock; > > > static volatile u8 *uart0_base = UART_EARLY_BASE; > > > bool is_pl011_uart; > > > +static inline volatile u8 *get_uart_base(void) > > > +{ > > > + /* > > > + * The address of the UART base may be different > > > + * based on whether we are running with/without > > > + * MMU enabled. > > > + * > > > + * For realms, we must force to use the shared physical > > > + * alias with MMU disabled, to make sure the I/O can > > > + * be emulated. > > > + * When the MMU is turned ON, the mappings are created > > > + * appropriately. > > > + */ > > > + if (mmu_enabled()) > > > + return uart0_base; > > > + return (u8 *)arm_shared_phys_alias((void *)uart0_base); > > > +} > > > + > > > static void uart0_init_fdt(void) > > > { > > > /* > > > @@ -109,9 +129,11 @@ void io_init(void) > > > void puts(const char *s) > > > { > > > + volatile u8 *uart_base = get_uart_base(); > > > + > > > spin_lock(&uart_lock); > > > while (*s) > > > - writeb(*s++, uart0_base); > > > + writeb(*s++, uart_base); > > > spin_unlock(&uart_lock); > > > } > > > diff --git a/lib/arm64/asm/pgtable.h b/lib/arm64/asm/pgtable.h > > > index 5b9f40b0..871c03e9 100644 > > > --- a/lib/arm64/asm/pgtable.h > > > +++ b/lib/arm64/asm/pgtable.h > > > @@ -28,6 +28,11 @@ extern unsigned long prot_ns_shared; > > > */ > > > #define PTE_NS_SHARED (prot_ns_shared) > > > +static inline unsigned long arm_shared_phys_alias(void *addr) > > > +{ > > > + return ((unsigned long)addr | PTE_NS_SHARED); > > > +} > > > + > > > /* > > > * Highest possible physical address supported. > > > */ > > > -- > > > 2.34.1 > > > > >