Hi, On Mon, Apr 22, 2024 at 01:23:05PM +0100, Alexandru Elisei wrote: > Hi, > > On Mon, Apr 22, 2024 at 01:09:13PM +0100, Suzuki K Poulose wrote: > > Hi Alexandru > > > > On 22/04/2024 12:58, Alexandru Elisei wrote: > > > Hi, > > > > > > On Fri, Apr 12, 2024 at 11:33:43AM +0100, Suzuki K Poulose wrote: > > > > From: Joey Gouly <joey.gouly@xxxxxxx> > > > > > > > > A Realm must access any emulated I/O mappings with the PTE_NS_SHARED bit set. > > > > 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 <joey.gouly@xxxxxxx> > > > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx> > > > > --- > > > > 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); > > > > +} > > > > > > Is it allowed for a realm to run in aarch32 mode? > > > > No. Realm EL1 must be Aarch64. > > Ok, then can you make the above function return the original address? > > > > > > > > > > + > > > > #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 <asm/psci.h> > > > > #include <asm/spinlock.h> > > > > #include <asm/io.h> > > > > +#include <asm/mmu-api.h> > > > > +#include <asm/pgtable.h> > > > > #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(); > > Is it just my email client or is the indentation missing here? > > > > > + > > > > 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); > > > > +} > > > > > > Have you considered specifying the correct UART address at compile time using > > > ./configure --earlycon? > > > > Do you mean > > > > ./configure --earlycon=<NS-Alias-normal-UART-Address> for Realms ? > > > > If so, there are multiple issues with that : > > > > 1. A payload could be run in a normal VM or a Realm VM. Having the above > > restricts using the same payload in different worlds. (e.g., comparison). > > > > 2. The IPA width of the Realm and thus the PTE_NS_SHARED is dynamic > > and really depends on what the VMM decides to choose the IPA size. > > (Could be based on user input). > > Does it depend on the chosen IPA size, or on the VA size, or on both? > Because uart0_base is used with both the MMU on and off. Oh, ok, my bad, I hadn't realized that the uart address is modified only if the MMU is not enabled. So it's actually only the IPA that must have the bit set. I have to say that a PTE attribute, as it is called in the commit message, which has a variable bit position that depends on the output address size is quite surprising. I was under the impression that the bit position is constant when I made the suggestion. Yeah, it makes sense to have a helper to set the bit based on whether or not the MMU is enabled. Thanks, Alex > > Thanks, > Alex > > > > > If any of the above fails, and a wrong earlycon address could result > > in "Synchronouse External Abort" into the Realm (if it is in protected > > IPA). > > > > Suzuki > > > > > > Thanks, > > > Alex > > > > + > > > > /* > > > > * Highest possible physical address supported. > > > > */ > > > > -- > > > > 2.34.1 > > > > > > >