Re: [Xen-devel] [PATCH 18/38] arm: implement vpl011 (UART) emulator.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-06-07 at 11:18 +0100, Tim Deegan wrote:
> At 10:34 +0100 on 07 Jun (1339065291), Ian Campbell wrote:
> > On Thu, 2012-06-07 at 10:29 +0100, Tim Deegan wrote:
> > > > +int domain_uart0_init(struct domain *d)
> > > > +{
> > > > +    int rc;
> > > > +    if ( d->domain_id == 0 )
> > > > +        return 0;
> > > 
> > > Why?  There's no equivalent gate on the MMIO handlers.
> > 
> > dom0 has the actual uart mapped at this address, not the emulated one.
> > Maybe that should be written at the caller instead?
> 
> Yes - ideally in the same place that puts the MMIO hooks in that will
> call the other functions in this file. 

Turns out that there isn't actually such a place, these are part of a
global list of mmio handlers which is traversed for any guest dabt.

This might be something we want to improve (using bits in not-present
p2m entries to identify specific handlers or whatever) but not right now
I think.

I've pulled the dom0 check out into the caller of the init function, but
left an ASSERT behind. I also shortened that long line by using a
#define for the end and removing the dom0 check from there too.

8<------------------------------------------------------------

>From 401e861ff99860d07e758c8d6e3260b8fb847fc5 Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Mon, 14 May 2012 12:55:31 +0100
Subject: [PATCH] arm: implement vpl011 (UART) emulator.

This is not interended to provide a full emulation, but rather just enough to
satisfy the use made by Linux' boot time decompressor code (which is too early
for DT etc)

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/arch/arm/Makefile        |    1 +
 xen/arch/arm/domain.c        |    5 ++
 xen/arch/arm/io.c            |    1 +
 xen/arch/arm/io.h            |    1 +
 xen/arch/arm/vpl011.c        |  145 ++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/vpl011.h        |   34 ++++++++++
 xen/include/asm-arm/domain.h |    8 ++
 7 files changed, 195 insertions(+), 0 deletions(-)
 create mode 100644 xen/arch/arm/vpl011.c
 create mode 100644 xen/arch/arm/vpl011.h

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 9440a21..5a87ba6 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -25,6 +25,7 @@ obj-y += shutdown.o
 obj-y += traps.o
 obj-y += vgic.o
 obj-y += vtimer.o
+obj-y += vpl011.o
 
 #obj-bin-y += ....o
 
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 63bad07..931261b 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -13,6 +13,7 @@
 
 #include "gic.h"
 #include "vtimer.h"
+#include "vpl011.h"
 
 DEFINE_PER_CPU(struct vcpu *, curr_vcpu);
 
@@ -215,6 +216,10 @@ int arch_domain_create(struct domain *d, unsigned int 
domcr_flags)
     if ( (rc = domain_vgic_init(d)) != 0 )
         goto fail;
 
+    /* Domain 0 gets a real UART not an emulated one */
+    if ( d->domain_id && (rc = domain_uart0_init(d)) != 0 )
+        goto fail;
+
     rc = 0;
 fail:
     return rc;
diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index 4461225..18f6164 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -25,6 +25,7 @@
 static const struct mmio_handler *const mmio_handlers[] =
 {
     &vgic_distr_mmio_handler,
+    &uart0_mmio_handler,
 };
 #define MMIO_HANDLER_NR ARRAY_SIZE(mmio_handlers)
 
diff --git a/xen/arch/arm/io.h b/xen/arch/arm/io.h
index 8cc5ca7..9a507f5 100644
--- a/xen/arch/arm/io.h
+++ b/xen/arch/arm/io.h
@@ -40,6 +40,7 @@ struct mmio_handler {
 };
 
 extern const struct mmio_handler vgic_distr_mmio_handler;
+extern const struct mmio_handler uart0_mmio_handler;
 
 extern int handle_mmio(mmio_info_t *info);
 
diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c
new file mode 100644
index 0000000..5dc8b28
--- /dev/null
+++ b/xen/arch/arm/vpl011.c
@@ -0,0 +1,145 @@
+/*
+ * xen/arch/arm/vpl011.c
+ *
+ * ARM PL011 UART Emulator (DEBUG)
+ *
+ * Ian Campbell <ian.campbell@xxxxxxxxxx>
+ * Copyright (c) 2012 Citrix Systems.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+/*
+ * This is not intended to be a full emulation of a PL011
+ * device. Rather it is intended to provide a sufficient veneer of one
+ * that early code (such as Linux's boot time decompressor) which
+ * hardcodes output directly to such a device are able to make progress.
+ *
+ * This device is not intended to be enumerable or exposed to the OS
+ * (e.g. via Device Tree).
+ */
+
+#include <xen/config.h>
+#include <xen/lib.h>
+#include <xen/sched.h>
+#include <xen/errno.h>
+#include <xen/ctype.h>
+
+#include "io.h"
+
+#define UART0_START 0x1c090000
+#define UART0_END   (UART0_START+65536)
+
+#define UARTDR 0x000
+#define UARTFR 0x018
+
+int domain_uart0_init(struct domain *d)
+{
+    ASSERT( d->domain_id );
+
+    spin_lock_init(&d->arch.uart0.lock);
+    d->arch.uart0.idx = 0;
+
+    d->arch.uart0.buf = xzalloc_array(char, VPL011_BUF_SIZE);
+    if ( !d->arch.uart0.buf )
+        return -ENOMEM;
+
+    return 0;
+
+}
+
+static void uart0_print_char(char c)
+{
+    struct vpl011 *uart = &current->domain->arch.uart0;
+
+    /* Accept only printable characters, newline, and horizontal tab. */
+    if ( !isprint(c) && (c != '\n') && (c != '\t') )
+        return ;
+
+    spin_lock(&uart->lock);
+    uart->buf[uart->idx++] = c;
+    if ( (uart->idx == (VPL011_BUF_SIZE - 2)) || (c == '\n') )
+    {
+        if ( c != '\n' )
+            uart->buf[uart->idx++] = '\n';
+        uart->buf[uart->idx] = '\0';
+        printk(XENLOG_G_DEBUG "DOM%u: %s",
+               current->domain->domain_id, uart->buf);
+        uart->idx = 0;
+    }
+    spin_unlock(&uart->lock);
+}
+
+static int uart0_mmio_check(struct vcpu *v, paddr_t addr)
+{
+    return addr >= UART0_START && addr < UART0_END;
+}
+
+static int uart0_mmio_read(struct vcpu *v, mmio_info_t *info)
+{
+    struct hsr_dabt dabt = info->dabt;
+    struct cpu_user_regs *regs = guest_cpu_user_regs();
+    uint32_t *r = &regs->r0 + dabt.reg;
+    int offset = (int)(info->gpa - UART0_START);
+
+    switch ( offset )
+    {
+    case UARTDR:
+        *r = 0;
+        return 1;
+    case UARTFR:
+        *r = 0x87; /* All holding registers empty, ready to send etc */
+        return 1;
+    default:
+        printk("VPL011: unhandled read r%d offset %#08x\n",
+               dabt.reg, offset);
+        domain_crash_synchronous();
+    }
+}
+
+static int uart0_mmio_write(struct vcpu *v, mmio_info_t *info)
+{
+    struct hsr_dabt dabt = info->dabt;
+    struct cpu_user_regs *regs = guest_cpu_user_regs();
+    uint32_t *r = &regs->r0 + dabt.reg;
+    int offset = (int)(info->gpa - UART0_START);
+
+    switch ( offset )
+    {
+    case UARTDR:
+        /* ignore any status bits */
+        uart0_print_char((int)((*r) & 0xFF));
+        return 1;
+    case UARTFR:
+        /* Silently ignore */
+        return 1;
+    default:
+        printk("VPL011: unhandled write r%d=%"PRIx32" offset %#08x\n",
+               dabt.reg, *r, offset);
+        domain_crash_synchronous();
+    }
+}
+
+const struct mmio_handler uart0_mmio_handler = {
+    .check_handler = uart0_mmio_check,
+    .read_handler  = uart0_mmio_read,
+    .write_handler = uart0_mmio_write,
+};
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
+
diff --git a/xen/arch/arm/vpl011.h b/xen/arch/arm/vpl011.h
new file mode 100644
index 0000000..952d812
--- /dev/null
+++ b/xen/arch/arm/vpl011.h
@@ -0,0 +1,34 @@
+/*
+ * xen/arch/arm/vpl011.h
+ *
+ * ARM PL011 Emulation Support
+ *
+ * Ian Campbell <ian.campbell@xxxxxxxxxx>
+ * Copyright (c) 2012 Citrix Systems.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __ARCH_ARM_VPL011_H__
+#define __ARCH_ARM_VPL011_H__
+
+extern int domain_uart0_init(struct domain *d);
+
+#endif
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 10ed540..f295a82 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -48,6 +48,14 @@ struct arch_domain
         struct vgic_irq_rank *shared_irqs;
         struct pending_irq *pending_irqs;
     } vgic;
+
+    struct vpl011 {
+#define VPL011_BUF_SIZE 128
+        char                  *buf;
+        int                    idx;
+        spinlock_t             lock;
+    } uart0;
+
 }  __cacheline_aligned;
 
 struct arch_vcpu
-- 
1.7.9.1




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