| Message ID | 20200608161353.2654-1-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [for-4.14,v4] x86/rtc: provide mediated access to RTC for PVH dom0 | expand |
> -----Original Message----- > From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of Roger Pau Monne > Sent: 08 June 2020 17:14 > To: xen-devel@lists.xenproject.org > Cc: Andrew Cooper <andrew.cooper3@citrix.com>; Roger Pau Monne <roger.pau@citrix.com>; Wei Liu > <wl@xen.org>; Jan Beulich <jbeulich@suse.com>; paul@xen.org > Subject: [PATCH for-4.14 v4] x86/rtc: provide mediated access to RTC for PVH dom0 > > Mediated access to the RTC was provided for PVHv1 dom0 using the PV > code paths (guest_io_{write/read}), but those accesses where never > implemented for PVHv2 dom0. This patch provides such mediated accesses > to the RTC for PVH dom0, just like it's provided for a classic PV > dom0. > > Pull out some of the RTC logic from guest_io_{read/write} into > specific helpers that can be used by both PV and HVM guests. The > setup of the handlers for PVH is done in rtc_init, which is already > used to initialize the fully emulated RTC. > > Without this a Linux PVH dom0 will read garbage when trying to access > the RTC, and one vCPU will be constantly looping in > rtc_timer_do_work. > > Note that such issue doesn't happen on domUs because the ACPI > NO_CMOS_RTC flag is set in FADT, which prevents the OS from accessing > the RTC. Also the X86_EMU_RTC flag is not set for PVH dom0, as the > accesses are not emulated but rather forwarded to the physical > hardware. > > No functional change expected for classic PV dom0. > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > Reviewed-by: Jan Beulich <jbeulich@suse.com> Release-acked-by: Paul Durrant <paul@xen.org> > --- > for-4.14 reasoning: the fix is mostly isolated to PVH dom0, and as > such the risk is very low of causing issues to other guests types, but > without this fix one vCPU when using a Linux dom0 will be constantly > looping over rtc_timer_do_work with 100% CPU usage, at least when > using Linux 4.19 or newer. > --- > Changes since v3: > - Reword comment. > - Add missing newline after break. > - Remove extra parentheses in the RTC ports check in > guest_io_{read/write}. > > Changes since v2: > - Move the access check into the read/write handler. > - Allow access to the latched first RTC port by all PV guests. > - Register the handlers for HVM native accesses if vRTC is disabled. > > Changes since v1: > - Share the code with PV. > - Add access checks to the IO ports. > --- > xen/arch/x86/hvm/rtc.c | 26 +++++++++++++ > xen/arch/x86/pv/emul-priv-op.c | 30 ++------------ > xen/arch/x86/time.c | 65 +++++++++++++++++++++++++++++++ > xen/include/asm-x86/mc146818rtc.h | 3 ++ > 4 files changed, 98 insertions(+), 26 deletions(-) > > diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c > index 5bbbdc0e0f..3150f5f147 100644 > --- a/xen/arch/x86/hvm/rtc.c > +++ b/xen/arch/x86/hvm/rtc.c > @@ -808,12 +808,38 @@ void rtc_reset(struct domain *d) > s->pt.source = PTSRC_isa; > } > > +/* RTC mediator for HVM hardware domain. */ > +static int hw_rtc_io(int dir, unsigned int port, unsigned int size, > + uint32_t *val) > +{ > + if ( dir == IOREQ_READ ) > + *val = ~0; > + > + if ( size != 1 ) > + { > + gdprintk(XENLOG_WARNING, "bad RTC access size (%u)\n", size); > + return X86EMUL_OKAY; > + } > + > + if ( dir == IOREQ_WRITE ) > + rtc_guest_write(port, *val); > + else > + *val = rtc_guest_read(port); > + > + return X86EMUL_OKAY; > +} > + > void rtc_init(struct domain *d) > { > RTCState *s = domain_vrtc(d); > > if ( !has_vrtc(d) ) > + { > + if ( is_hardware_domain(d) ) > + /* Hardware domain gets mediated access to the physical RTC. */ > + register_portio_handler(d, RTC_PORT(0), 2, hw_rtc_io); > return; > + } > > spin_lock_init(&s->lock); > > diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c > index fad6c754ad..254da2b849 100644 > --- a/xen/arch/x86/pv/emul-priv-op.c > +++ b/xen/arch/x86/pv/emul-priv-op.c > @@ -280,19 +280,9 @@ static uint32_t guest_io_read(unsigned int port, unsigned int bytes, > { > sub_data = pv_pit_handler(port, 0, 0); > } > - else if ( port == RTC_PORT(0) ) > + else if ( port == RTC_PORT(0) || port == RTC_PORT(1) ) > { > - sub_data = currd->arch.cmos_idx; > - } > - else if ( (port == RTC_PORT(1)) && > - ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) > - { > - unsigned long flags; > - > - spin_lock_irqsave(&rtc_lock, flags); > - outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); > - sub_data = inb(RTC_PORT(1)); > - spin_unlock_irqrestore(&rtc_lock, flags); > + sub_data = rtc_guest_read(port); > } > else if ( (port == 0xcf8) && (bytes == 4) ) > { > @@ -413,21 +403,9 @@ static void guest_io_write(unsigned int port, unsigned int bytes, > { > pv_pit_handler(port, (uint8_t)data, 1); > } > - else if ( port == RTC_PORT(0) ) > - { > - currd->arch.cmos_idx = data; > - } > - else if ( (port == RTC_PORT(1)) && > - ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) > + else if ( port == RTC_PORT(0) || port == RTC_PORT(1) ) > { > - unsigned long flags; > - > - if ( pv_rtc_handler ) > - pv_rtc_handler(currd->arch.cmos_idx & 0x7f, data); > - spin_lock_irqsave(&rtc_lock, flags); > - outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); > - outb(data, RTC_PORT(1)); > - spin_unlock_irqrestore(&rtc_lock, flags); > + rtc_guest_write(port, data); > } > else if ( (port == 0xcf8) && (bytes == 4) ) > { > diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c > index bbaea3aa65..d643590c0a 100644 > --- a/xen/arch/x86/time.c > +++ b/xen/arch/x86/time.c > @@ -27,6 +27,7 @@ > #include <xen/keyhandler.h> > #include <xen/guest_access.h> > #include <asm/io.h> > +#include <asm/iocap.h> > #include <asm/msr.h> > #include <asm/mpspec.h> > #include <asm/processor.h> > @@ -1110,6 +1111,70 @@ static unsigned long get_cmos_time(void) > return mktime(rtc.year, rtc.mon, rtc.day, rtc.hour, rtc.min, rtc.sec); > } > > +/* Helpers for guest accesses to the physical RTC. */ > +unsigned int rtc_guest_read(unsigned int port) > +{ > + const struct domain *currd = current->domain; > + unsigned long flags; > + unsigned int data = ~0; > + > + switch ( port ) > + { > + case RTC_PORT(0): > + /* > + * All PV domains (and PVH dom0) are allowed to read the latched value > + * of the first RTC port, as there's no access to the physical IO > + * ports. > + */ > + data = currd->arch.cmos_idx; > + break; > + > + case RTC_PORT(1): > + if ( !ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) > + break; > + spin_lock_irqsave(&rtc_lock, flags); > + outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); > + data = inb(RTC_PORT(1)); > + spin_unlock_irqrestore(&rtc_lock, flags); > + break; > + > + default: > + ASSERT_UNREACHABLE(); > + } > + > + return data; > +} > + > +void rtc_guest_write(unsigned int port, unsigned int data) > +{ > + struct domain *currd = current->domain; > + unsigned long flags; > + > + switch ( port ) > + { > + case RTC_PORT(0): > + /* > + * All PV domains (and PVH dom0) are allowed to write to the latched > + * value of the first RTC port, as there's no access to the physical IO > + * ports. > + */ > + currd->arch.cmos_idx = data; > + break; > + > + case RTC_PORT(1): > + if ( !ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) > + break; > + spin_lock_irqsave(&rtc_lock, flags); > + outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); > + outb(data, RTC_PORT(1)); > + spin_unlock_irqrestore(&rtc_lock, flags); > + break; > + > + default: > + ASSERT_UNREACHABLE(); > + } > +} > + > static unsigned long get_wallclock_time(void) > { > #ifdef CONFIG_XEN_GUEST > diff --git a/xen/include/asm-x86/mc146818rtc.h b/xen/include/asm-x86/mc146818rtc.h > index 8758528f7c..803b236c0a 100644 > --- a/xen/include/asm-x86/mc146818rtc.h > +++ b/xen/include/asm-x86/mc146818rtc.h > @@ -110,4 +110,7 @@ outb_p((val),RTC_PORT(1)); \ > > #define RTC_IRQ 8 > > +unsigned int rtc_guest_read(unsigned int port); > +void rtc_guest_write(unsigned int port, unsigned int data); > + > #endif /* _ASM_MC146818RTC_H */ > -- > 2.26.2 >
diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c index 5bbbdc0e0f..3150f5f147 100644 --- a/xen/arch/x86/hvm/rtc.c +++ b/xen/arch/x86/hvm/rtc.c @@ -808,12 +808,38 @@ void rtc_reset(struct domain *d) s->pt.source = PTSRC_isa; } +/* RTC mediator for HVM hardware domain. */ +static int hw_rtc_io(int dir, unsigned int port, unsigned int size, + uint32_t *val) +{ + if ( dir == IOREQ_READ ) + *val = ~0; + + if ( size != 1 ) + { + gdprintk(XENLOG_WARNING, "bad RTC access size (%u)\n", size); + return X86EMUL_OKAY; + } + + if ( dir == IOREQ_WRITE ) + rtc_guest_write(port, *val); + else + *val = rtc_guest_read(port); + + return X86EMUL_OKAY; +} + void rtc_init(struct domain *d) { RTCState *s = domain_vrtc(d); if ( !has_vrtc(d) ) + { + if ( is_hardware_domain(d) ) + /* Hardware domain gets mediated access to the physical RTC. */ + register_portio_handler(d, RTC_PORT(0), 2, hw_rtc_io); return; + } spin_lock_init(&s->lock); diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c index fad6c754ad..254da2b849 100644 --- a/xen/arch/x86/pv/emul-priv-op.c +++ b/xen/arch/x86/pv/emul-priv-op.c @@ -280,19 +280,9 @@ static uint32_t guest_io_read(unsigned int port, unsigned int bytes, { sub_data = pv_pit_handler(port, 0, 0); } - else if ( port == RTC_PORT(0) ) + else if ( port == RTC_PORT(0) || port == RTC_PORT(1) ) { - sub_data = currd->arch.cmos_idx; - } - else if ( (port == RTC_PORT(1)) && - ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) - { - unsigned long flags; - - spin_lock_irqsave(&rtc_lock, flags); - outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); - sub_data = inb(RTC_PORT(1)); - spin_unlock_irqrestore(&rtc_lock, flags); + sub_data = rtc_guest_read(port); } else if ( (port == 0xcf8) && (bytes == 4) ) { @@ -413,21 +403,9 @@ static void guest_io_write(unsigned int port, unsigned int bytes, { pv_pit_handler(port, (uint8_t)data, 1); } - else if ( port == RTC_PORT(0) ) - { - currd->arch.cmos_idx = data; - } - else if ( (port == RTC_PORT(1)) && - ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) + else if ( port == RTC_PORT(0) || port == RTC_PORT(1) ) { - unsigned long flags; - - if ( pv_rtc_handler ) - pv_rtc_handler(currd->arch.cmos_idx & 0x7f, data); - spin_lock_irqsave(&rtc_lock, flags); - outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); - outb(data, RTC_PORT(1)); - spin_unlock_irqrestore(&rtc_lock, flags); + rtc_guest_write(port, data); } else if ( (port == 0xcf8) && (bytes == 4) ) { diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index bbaea3aa65..d643590c0a 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -27,6 +27,7 @@ #include <xen/keyhandler.h> #include <xen/guest_access.h> #include <asm/io.h> +#include <asm/iocap.h> #include <asm/msr.h> #include <asm/mpspec.h> #include <asm/processor.h> @@ -1110,6 +1111,70 @@ static unsigned long get_cmos_time(void) return mktime(rtc.year, rtc.mon, rtc.day, rtc.hour, rtc.min, rtc.sec); } +/* Helpers for guest accesses to the physical RTC. */ +unsigned int rtc_guest_read(unsigned int port) +{ + const struct domain *currd = current->domain; + unsigned long flags; + unsigned int data = ~0; + + switch ( port ) + { + case RTC_PORT(0): + /* + * All PV domains (and PVH dom0) are allowed to read the latched value + * of the first RTC port, as there's no access to the physical IO + * ports. + */ + data = currd->arch.cmos_idx; + break; + + case RTC_PORT(1): + if ( !ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) + break; + spin_lock_irqsave(&rtc_lock, flags); + outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); + data = inb(RTC_PORT(1)); + spin_unlock_irqrestore(&rtc_lock, flags); + break; + + default: + ASSERT_UNREACHABLE(); + } + + return data; +} + +void rtc_guest_write(unsigned int port, unsigned int data) +{ + struct domain *currd = current->domain; + unsigned long flags; + + switch ( port ) + { + case RTC_PORT(0): + /* + * All PV domains (and PVH dom0) are allowed to write to the latched + * value of the first RTC port, as there's no access to the physical IO + * ports. + */ + currd->arch.cmos_idx = data; + break; + + case RTC_PORT(1): + if ( !ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) ) + break; + spin_lock_irqsave(&rtc_lock, flags); + outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0)); + outb(data, RTC_PORT(1)); + spin_unlock_irqrestore(&rtc_lock, flags); + break; + + default: + ASSERT_UNREACHABLE(); + } +} + static unsigned long get_wallclock_time(void) { #ifdef CONFIG_XEN_GUEST diff --git a/xen/include/asm-x86/mc146818rtc.h b/xen/include/asm-x86/mc146818rtc.h index 8758528f7c..803b236c0a 100644 --- a/xen/include/asm-x86/mc146818rtc.h +++ b/xen/include/asm-x86/mc146818rtc.h @@ -110,4 +110,7 @@ outb_p((val),RTC_PORT(1)); \ #define RTC_IRQ 8 +unsigned int rtc_guest_read(unsigned int port); +void rtc_guest_write(unsigned int port, unsigned int data); + #endif /* _ASM_MC146818RTC_H */
Mediated access to the RTC was provided for PVHv1 dom0 using the PV code paths (guest_io_{write/read}), but those accesses where never implemented for PVHv2 dom0. This patch provides such mediated accesses to the RTC for PVH dom0, just like it's provided for a classic PV dom0. Pull out some of the RTC logic from guest_io_{read/write} into specific helpers that can be used by both PV and HVM guests. The setup of the handlers for PVH is done in rtc_init, which is already used to initialize the fully emulated RTC. Without this a Linux PVH dom0 will read garbage when trying to access the RTC, and one vCPU will be constantly looping in rtc_timer_do_work. Note that such issue doesn't happen on domUs because the ACPI NO_CMOS_RTC flag is set in FADT, which prevents the OS from accessing the RTC. Also the X86_EMU_RTC flag is not set for PVH dom0, as the accesses are not emulated but rather forwarded to the physical hardware. No functional change expected for classic PV dom0. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> --- for-4.14 reasoning: the fix is mostly isolated to PVH dom0, and as such the risk is very low of causing issues to other guests types, but without this fix one vCPU when using a Linux dom0 will be constantly looping over rtc_timer_do_work with 100% CPU usage, at least when using Linux 4.19 or newer. --- Changes since v3: - Reword comment. - Add missing newline after break. - Remove extra parentheses in the RTC ports check in guest_io_{read/write}. Changes since v2: - Move the access check into the read/write handler. - Allow access to the latched first RTC port by all PV guests. - Register the handlers for HVM native accesses if vRTC is disabled. Changes since v1: - Share the code with PV. - Add access checks to the IO ports. --- xen/arch/x86/hvm/rtc.c | 26 +++++++++++++ xen/arch/x86/pv/emul-priv-op.c | 30 ++------------ xen/arch/x86/time.c | 65 +++++++++++++++++++++++++++++++ xen/include/asm-x86/mc146818rtc.h | 3 ++ 4 files changed, 98 insertions(+), 26 deletions(-)